Chapter VIII: Chinese Literature (5)

The _Phyllostomatidae_ are characterized by the presence of a
nose-leaf, or of lappets on the chin, but the nostrils are not
directed upwards. The ethmoturbinal bones of the nasal cavity form
simple plates (much as in the two preceding families). The premaxillae
are always well developed, with their palatal portions forming a
suture and denning the boundaries of distinct palatine foramina (in
place of being rudimentary, as in _Nycteridae_ and _Rhinolophidae_).
The large ears have a tragus. The middle finger has three phalanges,
and the index one. There is an incomplete fibula. The tail may be
either long or short. Generally the dentition is _i._ 2/2, _c._ 1/1,
_p._ 2/3, _m._ 3/3.

All the bats of this family may be readily recognized by the presence
of a well-developed third phalange in the middle finger, associated
either with a distinct nose-leaf, or with central upper incisors, or
with both. Unlike the _Rhinolophidae_, their eyes are generally large
and the tragus is well developed, maintaining almost the same form
throughout the species, however much the other parts of the body may
vary. Their fur is of a dull colour, and the face and back are often
marked with white streaks. A few species, probably all those with the
tail and interfemoral membrane well developed, feed principally on
insects, while the greater number of the species of the groups
_Vampyreae_ and _Glossophageae_ appear to live on a mixed diet of
insects and fruits, and the _Desmodonteae_, of which two species are
known, are true blood-suckers, and have their teeth and intestinal
tract specially modified in accordance with their habits. The group is
practically limited to the tropical and subtropical parts of Central
and South America, although one species of _Otopterus_ reaches
California. In the first subfamily, _Mormopsinae_ (_Lobostominae_),
the nostrils open by simple apertures at the extremity of the muzzle
in front, not margined by a distinct nose-leaf; while, in
compensation, the chin is furnished with expanded leaf-like
appendages. The tail is short. It includes two genera. In
_Chilonycteris_ the crown of the head is moderately elevated above the
face-line, and the basi-cranial axis is almost in the same plane as
the facial, while in _Mormops_ (fig. 10) the crown of the head is
greatly elevated above the face-line, and the basi-cranial axis is
nearly at right angles to the facial; _i._ 2/2, _p._ 2/3, in both
genera. As regards the species of _Chilonycteris_, the most striking
feature is the occurrence of a rufous and a dark brown phase in each.
In some the two phases are very marked, but in others they are
connected by intermediate shades. Here may be mentioned the two
species of tropical American hare-lipped bats, forming the genus
_Noctilio_, which presents characters common to this and the following
family, to which latter it is often referred. The typical _N.
leporinus_ is a bat of curious aspect, with strangely folded lips,
erect skin-processes on the chin, and enormous feet and claws. The two
middle incisors are close together, and so large as to conceal the
small outer ones, while in the lower jaw there are but two small
incisors; the premolars numbering 1/2. These bats live near the coast,
and feed on small crabs and fishes.

Most of the remaining members of the family are included in the
subfamily _Phyllostomatinae_, characterized by the presence of a
distinct nose-leaf and the warty chin. The clitoris is imperforate,
whereas it is perforated in the _Mormopsinae_. The incisors are
generally 2/2 (occasionally 2/1), and the molars well developed. The
subfamily is divided into a number of groups or sections. The first of
them, the _Vampyreae_, is characterized as follows: Muzzle long and
narrow in front, the distance between the eyes generally less than
(rarely equal to) that from the eye to the extremity of the muzzle;
nose-leaf horseshoe-shaped in front, lanceolate behind; interfemoral
membrane well developed; tail generally distinct, rarely absent; inner
margin of the lips not fringed; _i._ 2/2 or 2/1, _p._ 2/2 or 2/3;
molars with W-shaped cusps, usually well developed.

Nearly all the _Vampyreae_ appear to be insectivorous, so that the
term cannot be considered indicative of habits; but a few, if not all,
probably supplement their insect diet with fruit. _Vampyrus spectrum_
(the largest bat in the New World) is said to be wholly frugivorous,
and _Otopterus waterhousei_ appears to prey occasionally on smaller
bats. The genera may be arranged in two subgroups according as the
tail is produced to the margin of the interfemoral membrane or
perforates it to appear on its upper surface. In the first division
are included three genera, _Lonchorhina_, _Otopterus_ (or _Macrotus_)
and _Dolichophyllum_ (or _Macrophyllum_), the first represented by _L.
aurita_, characterized by an extraordinary long nose-leaf, and
peculiarly large ears and tragus. In the second subsection are
included _Vampyrus_, _Chrotopterus_, _Tonatia_ (_Lophostoma_)
_Micronycteris_, _Glyphonycteris_, _Trachyops_, _Phylloderma_,
_Phyllostoma_, _Anthorhina_ (_Tylostoma_), _Mimon_, _Hemiderma_
(_Carollia_) and _Rhinophylla_; all, with the exception of the last,
distinguished chiefly by the form of the skull and the presence or
absence of the second lower premolar. _Phyllostoma hastatum_, next in
point of size to _Vampyrus spectrum_, is a well-known species in South
America; _P. elongatum_ (fig. 11) differs in its smaller size and
larger nose-leaf. _Hemiderma brevicauda_, a small species, closely
resembles _Glossophaga soricina_, and forms a connecting link between
this and the next group. _Rhinophylla pumilio_ is the smallest species
of the family; further distinguished by the absence of a tail, the
narrowness of its molars, which do not form W-shaped cusps, and the
small size of the last upper molar, characters connecting it and the
group with the _Stenodermateae_. Both in _Hemiderma_ and _Rhinophylla_
the zygomatic arch is incomplete.

The next subsection, _Glossophageae_, presents the following
distinctive features: Muzzle long and narrow; tongue long and
extensible, attenuated towards the tip, and beset with long filiform
recurved papillae; lower lip with a wide groove above, and in front
margined by small warts; nose-leaf small; tail short or none; _i._
2/2, _p._ 2/3 or 3/3 or 2/2, _m._ 3/3 or 2/3 or 2/2; teeth narrow;
molars with narrow W-shaped cusps, sometimes indistinct or absent;
lower incisors small or deciduous. The species included in this group
represent some ten genera, distinguished principally by differences in
the form and number of the teeth, and the presence or absence of the
zygomatic, arch of the skull. In _Glossophaga_ and _Phyllonycteris_
the upper incisors form a continuous row between the canines. In
_Monophyllus_ and _Leptonycteris_ (_Ischnoglossa_) they are separated
into pairs by a narrow interval in front; while in _Lonchoglossa_,
_Glossonycteris_ and _Choeronycteris_ they are widely separated and
placed in pairs near the canines. In the first four of these genera
the lower incisors are present (at least to a certain age), in the
last three they are deciduous even in youth. The zygomatic arch is
wanting in _Phyllonycteris_, _Glossonycteris_ and _Choeronycteris_.
The typical species is _Glossophaga soricina_, which, as already
mentioned, closely resembles _Hemiderma brevicauda_, both in form
and dentition. Its long brush-tipped tongue (which it possesses in
common with other species of the group) is used to lick out the pulpy
contents of fruits having hard rinds. The food of the species of this
group appears to consist of both fruit and insects, and the long
tongue may be used for extracting the latter from the deep corollas of
flowers. Other genera are _Lonchophylla_, _Rhithronycteris_,
_Hylonycteris_ and _Lychonycteris_, each with a single species (in
1904).

The third group, _Stenodermateae_, presents the following
characteristics:--Muzzle very short and generally broad in front, the
distance between the eyes nearly always exceeding (rarely equalling)
the distance from the eye to the extremity of the muzzle; nose-leaf
short, horseshoe-shaped in front, lanceolate behind (except in
_Brachyphylla_ and _Centurio_); interfemoral membrane concave behind;
tail none; inner margin of the lips fringed with conical papillae;
_i._ 2/2 or 2/1, _p._ 2/2, _m._ 3/3 or 2/3 or 2/2; cheek-teeth broad
(except in _Sturnira_), molars with concave or flat crowns margined
externally by raised cutting-edges. Although the _Stenodermateae_ are
generally easily distinguished from the _Vampyreae_ by the shortness
and breadth of the muzzle and the form of the cheek-teeth, certain
species of the latter resemble the former in external appearance,
agreeing almost absolutely in the form of the nose-leaf, the ears and
the tragus, and the warts on the chin. These resemblances show that,
while the form of the teeth and jaws has become modified to suit the
food, the external characters have remained much the same, and
indicate the common origin of the two sections. The food of these bats
appears to be wholly or in great part fruit. The species are divided
into some eleven genera, mostly distinguished by the form of the skull
and teeth. _Artibeus_ includes the frugivorous _A. perspicillatus_.
_Stenoderma achradophilum_, found in Jamaica and Cuba, with the last,
from which it is scarcely distinguishable externally except by its
much smaller size, differs in the absence of the horizontal plate of
the premaxillae on the palate. _Sturnira lilium_, while agreeing with
these in the form of the nose-leaf and ears, differs from all the
species of the family in its longitudinally-grooved molars, which
resemble those of the _Pteropodidae_ more closely than those of any
other bats; and the presence of tufts of long differently-coloured
hairs over glands in the sides of the neck is another character in
common with that group. _Centurio senex_ (fig. 13) is the type of a
small genus distinguished from _Stenoderma_ and other genera of this
group by the absence of a distinct nose-leaf. Some naturalists make
this genus the type of a distinct subgroup, _Centurioneae_. Up to 1904
the genera, exclusive of _Centurio_, included in the _Stenodermateae_
were _Artibeus_ (with several sub-genera), _Vampyrops_ (also with
subgenera), _Mesophylla_, _Chiroderma_, _Stenoderma_ (with 3
subgenera), _Ectophylla_, _Ametrida_ (with 2 sub-genera), _Pygoderma_,
_Sturnira_ and _Brachyphylla_.

The third subfamily, _Desmodontieae_, is represented only by the
blood-sucking bats, and distinguished by having _i._ 1/2, of which the
upper pair are cutting, the rudimentary molars, the very short
interfemoral membrane, and the blood-sucking habit. They are further
characterized as follows: Muzzle short and conical; nose-leaf
distinct; _p._ 2/3, _m._ 1/1 or 0/0; upper incisors occupying the
whole space between the canines; premolars narrow, with sharp-edged
longitudinal crowns; molars rudimentary or absent; stomach elongated,
and intestiniform. There are two genera, _Desmodus_, without calcar or
molars, and _Diphylla_, with a short calcar and a single rudimentary
molar on each side--restricted to Central and South America. _Desmodus
rufus_, the commoner species, is a little larger than the noctule bat,
and abundant in certain parts of South America, where it is
troublesome owing to its attacks upon domestic animals, sucking their
blood and leaving them weakened from repeated bleedings. (See
VAMPIRE.)

Free-tailed bats.

The fourth family of bats, unlike any of the three previous ones, has
a cosmopolitan distribution. These free-tailed bats, as they are
conveniently called, constituting the family _Emballonuridae_, present
the following distinctive features. The nostrils are of normal form
and without a nose-leaf. The premaxillae have their palatal portion
imperfectly developed, and united by a slender process with the
maxillae. The ears are large, with a small tragus. The middle finger
has two phalanges, and the index generally a single one. The fibula is
incomplete. The tail is generally short, and always partly free from
the interfemoral membrane. There is generally only a single pair of
upper incisors, separated by gaps from the canines, and from one
another in the middle line.

The distinctive feature of these bats is the free tail-tip, which
pierces the interfemoral membrane to appear on its upper surface, and
may project beyond its margin. As a rule, these bats may also be
recognized by the peculiar form of the muzzle, which is obliquely
truncated, the nostrils projecting more or less in front beyond the
lower lip, by the first phalange of the middle finger being folded in
repose forwards on the upper surface of the metacarpal bone, and by
the upper incisors. Although cosmopolitan, these bats rarely extend
north or south of the thirtieth parallels of latitude.

The family may be divided into two subfamilies, of which the
_Emballonurinae_ is characterized by the incomplete premaxillae, the
presence of only one phalange in the index finger, and the short tail.
The dental formula is generally _i._ 1/3 (sometimes 2/3 or 1/2), _c._
1/1, _p._ 2/3, _m._ 3/3. This subfamily may be further subdivided into
subgroups or sections of which the first, _Embalionurae_, is
characterized by the slender tail perforating the interfemoral
membrane, so as to appear on its upper surface; the legs long, with a
slender fibula; the incisors weak; and the premolars 2/2. The typical
genus _Emballonura_ presents the following features: _i._ 2/3,
extremity of the muzzle more or less produced beyond the lower lip,
forehead flat. The genus contains several species, inhabiting islands
from Madagascar through the Malay Archipelago and Siam to the
Navigator Islands. _Coleura_, with _i._ 1/3, the extremity of the
muzzle broad, and the forehead concave, has two species from East
Africa and the Seychelles. _Rhynchonycteris_ is distinguished from
_Coleura_ by the produced extremity of the muzzle. The single species,
_R. naso_, from Central and South America, is common in the vicinity
of streams, where it is usually found during the day resting on the
vertical faces of rocks, or on trunks of trees growing over water; it
escapes notice owing to the greyish colour of the fur of the body and
of small tufts on the antebrachial membrane counterfeiting the
weathered surfaces of rocks and bark. As evening approaches it appears
on the wing, flying close to the water. _Saccopteryx_ has _i._ 1/3 and
the antibrachial membrane with a pouch opening on its upper surface;
it contains several species from Central and South America. This sac
is developed only in the male and in the female is rudimentary. In
adult males a valvular longitudinal opening occupies the upper surface
of the membrane leading into a small pouch, the interior of which is
lined with a glandular membrane secreting an unctuous reddish
substance with a strong ammoniacal odour. Allied genera are the
tropical American _Peropteryx_ and the Brazilian _Cormura_. The
various species of tomb-bats (_Taphozous_) inhabit the tropical and
subtropical parts of all the eastern hemisphere except Polynesia, and
are distinguished by the cartilaginous premaxillaries, the deciduous
pair of upper incisors, and the presence of only two pairs of lower
incisors. Most of the species have a glandular sac (fig. 15) between
the angles of the lower jaw, more developed in males than in females,
in some species absent in the latter. An open throat-sac is wanting in
_T. melanopogon_, but about its position are the openings of small
pores, the secretion from which probably causes the hairs to grow
long, forming the black beard found in many males. The three tropical
American white bats, _Diclidurus_, with _i._ 1/3, _c._ 1/1, _p._ 3/2,
_m._ 3/3, resemble _Taphozous_ in the form of the head and ears, but,
besides other characters, differ from all other bats in possessing a
pouch, opening off the centre of the interior surface of the
interfemoral membrane; the extremity of the tail enters this, and
perforates its base.

The second subfamily of the _Emballonuridae_, _Rhinopomatinae_, is
represented only by the genus _Rhinopoma_, with several species
ranging from Egypt through Arabia to India, Burma and Sumatra. The
premaxillae (fig. 16) are complete; the index finger has two
phalanges; the tail is very long and mouselike; and the dental formula
_i._ 1/2, _c._ 1/1, _p._ 1/2, _m._ 2/3. Dr G.E. Dobson has remarked
that these mouse-tailed bats might be elevated to the rank of a
family, for it is difficult to determine their affinities, a kind of
cross relationship attaching them to the _Nycteridae_ on the one hand
and to the _Emballonuridae_ on the other. These bats, distinguished
from all other Microchiroptera by the presence of two phalanges in the
index finger and the long and slender tail projecting far beyond the
narrow interfemoral membrane, inhabit the subterranean tombs in Egypt
and deserted buildings generally from north-east Africa to Burma and
Sumatra.

Typical bats.

The last group, according to the system adopted by Prof. Max Weber, is
that of the _Vespertilionidae_, which includes such typical bats as
the pipistrelle, the noctule, and the long-eared species. By Mr G.S.
Miller[1] the first section of the family--_Natalinae_--is regarded as
of family rank, while the last section, or _Molossinae_, is included
by Dr G.E. Dobson in the _Emballonuridae_, from the typical forms of
which its members differ widely in tail-structure. In this extended
sense the family, which has a cosmopolitan distribution, may be
defined as follows:--The nostrils are normal and without a nose-leaf.
The ethmoturbinal bones of the nasal chamber are involuted. The
palatine processes of the premaxillae do not form a suture. The ear is
mostly large, with a tragus. The middle finger (except in
_Thyroptera_) has two phalanges. The fibula is usually rudimentary.
The tail is long and does not perforate the interfemoral membrane. The
incisors are generally 2/3 or 1/2, but may be reduced to 1/1 in the
_Molossinae_.

In the first subfamily, _Natalinae_, which is exclusively tropical
American, the other upper incisors are separated from one another and
from the canines; palatine processes of the premaxillae are at least
partially developed; and the dental formula is _i._ 2/3, _c._ 1/1,
_p._ {2 or 3}/3, _m._ 3/3. In general appearance these bats recall the
more typical _Vespertilionidae_, although the form of the muzzle is
suggestive of the _Mormopsinae_ among the _Phyllostomatidae_. Again,
while the form of the skull is vespertilione, the relation of the
vomer to the front end of the premaxillae is of the phyllostomine
type. The molars and incisors are likewise vespertilione, whereas the
premolars are as distinctly phyllostomine. Finally, while the third,
or middle, finger normally has two phalanges, as in typical
_Vespertilionidae_, the second of these is elongated and in
_Thyroptera_ divided into two, as in _Phyllostomatidae_.

The first two genera, _Furipterus_ and _Amorphochilus_, each have a
single species, the latter being distinguished from the former by the
wide separation of the nostrils and the backward prolongation of the
palate. In both the crown of the head is elevated, the thumb and first
phalange of the middle finger are very short, and the premolars are
2/3. The same elevation of the crown characterizes the genera
_Natalus_ and _Chilonatalus_ (fig. 17), in which the premolars are
3/3: in general appearance these bats are very like the Old World
vespertilionine genus _Cerivoula_, except for the short triangular
tragus. Lastly, _Thyroptera_ includes two species distinguished by an
additional phalange in the middle finger and by accessory
clinging-organs attached to the extremities. In _Thyroptera tricolor_,
_i._ 2/3, _p._ 3/3, from Brazil, these have the appearance of small,
circular, stalked, hollow disks (fig. 18), resembling miniature
sucking-cups of cuttle-fishes, and are attached to the inferior
surfaces of the thumbs and the soles of the feet. By their aid the bat
is able to maintain its hold when creeping over smooth vertical
surfaces.

The second or typical subfamily, _Vespertilioninae_, includes all the
remaining members of the family with the exception of the aberrant
_Molossinae_. The upper incisors are in proximity to the canines; the
premaxillae widely separated; the ears medium or large; the dental
formula is _i._ 2/3 (or 1/3), _c._ 1/1, _p._ 3/3 (2/3, 2/2, or 1/2),
_m._ 3/3; and the fibula very small and imperfect. All the members of
this large cosmopolitan group are closely allied, and differ chiefly
by external characters. They may be divided into subgroups. In the
first of these, the _Plecoteae_, of which the long-eared bat
(_Plecotus auritus_) is the type, the crown of the head is but
slightly raised above the face-line, the upper incisors are close to
the canines, and the nostrils are margined behind by grooves an the
upper surface of the muzzle, or by rudimentary nose-leaves; the ears
being generally very large and united. Of the six genera, _Plecotus_,
with _i._ 2/3, _p._ 2/3, has three species:--one the long-eared
European bat referred to above; _P. macrotis_, restricted to North
America, is distinguished by the great size of the glandular
prominences of the sides of the muzzle, which meet in the centre above
and behind the nostrils; the third species being also American. The
second, _Barbastella_, with _i._ 2/3, _p._ 2/2, distinguished by its
dentition and by the outer margin of the ear being carried forwards
above the mouth and in front of the eye, includes the European
barbastelle bat, _B. barbastellus_, and _B. darjelingensis_ from the
Himalaya. _Otonycteris_, _i._ 1/3, _pm._, 1/2, connecting this group
with the _Vespertilioneae_, is represented by _O. hemprichii_, from
North Africa and the Himalaya, and an Arabian species. The next two
genera are distinguished by the presence of a rudimentary nose-leaf:
_Nyctophilus_, _i._ 1/3, _p._ 1/2, with three species from
Australasia; and _Antrozous_, _i._ 1/2, _p._ 1/2, distinguished from
all the other members of the subfamily by having but two lower
incisors, and from other _Plecoteae_ by the separate ears; the two
species inhabit California. The sixth genus, _Euderma_, is also
represented by a Californian species.

The second group _Vespertilioneae_, with about thirteen genera,
includes the great majority of the species; and a large number of
these may be classed under _Vespertilio_, which is divisible into
subgenera, differing from one another in the number of premolars, and
often ranked as separate genera. One group is represented by _V._
(_Histiolus_) _magellanicus_, a species remarkable for its extreme
southern range, its relatives being also South American. A second
group, with _p._ 1/2, includes the British serotine, _V._
(_Eptesicus_) _serotinus_, of Europe and northern Asia, and
represented in North America by the closely allied _V._ (_E._)
_fuscus_. In the typical group, which includes the Old World _V.
murinus_, one species, _V. borealis_, ranges to the Arctic circle. The
European noctule, _V._ (_Pierygistes_) _noctula_, and Leisler's bat,
_V._ (_P._) _leisleri_, represent another group; and the common
pipistrelle, _V._ (_Pipistrellus_) _pipistrellus_, yet another, with
_p._ 2/2. The only other group that need be mentioned is one
represented by the North American _V._ (_Lasionycteris_)
_noctivagans_, with _p._ 2/3. The African _Laeephotes_, the Chinese
_Ia_, and the Papuan _Philetor_ are allied genera, each with a single
species. _Chalinolobus_ and _Glauconycteris_ have the same general
dental character as _Vespertilio_, but are distinguished by the
presence of a lobe projecting from the lower lip near the gape; the
former, with _p._ 2/2, is represented by five Australasian species,
one of which extends into New Zealand; while the latter, with _p._
1/2, is African. The species of _Glauconycteris_ are noticeable for
their peculiarly thin membranes traversed by distinct reticulations
and parallel lines. _Scotophilus_, with _i._ 1/3, _p._ 1/2, includes
several species, restricted to the tropical and subtropical regions of
the eastern hemisphere, though widely distributed within these limits.
These bats, though approaching certain species of _Vespertilio_ in
many points, are distinguished by the single (in place of two) pair of
unicuspidate upper incisors separated by a wide space and placed close
to the canines, by the small transverse first lower premolar crushed
in between the canine and second premolar, and, generally, by their
conical, nearly naked, muzzles and thick leathery membranes. _S.
temmincki_ is the commonest bat in India, and appears often before the
sun has touched the horizon. _S. gigas_, from equatorial Africa, is
the largest species. _Nycticejus_, with the same dental formula as
_Scotophilus_, is distinguished, by the first lower premolar not being
crushed in between the adjoining teeth, and the comparatively greater
size of the last upper molar. It includes only the North American _N.
humeralis_ (_crepuscularis_), a bat scarcely larger than the
pipistrelle. The hairy-membraned bats of the genus _Lasiurus_
(_Atalapha_), with _i._ 1/3, _p._ 2/2 or 1/2, are also limited to the
New World, and generally characterized by the interfemoral membrane
being more or less covered with hair and by the peculiar form of the
tragus, which is expanded above and abruptly curved inwards. In those
species which have two upper premolars the first is extremely small
and internal to the tooth-row. The genus, which is divided into
_Lasiurus_ proper and _Dasypterus_, is further characterized by the
presence of four teats in the female, and by the general production
of three or four offspring at a birth. _Rhogeessa_ and _Tomopeas_ are
allied tropical American types. _Murina_, with the subgenus
_Harpiocephalus_, has _i._ 2/3, _p._ 2/2, and includes several small
bats distinguished by the prominent tube-like nostrils and hairy
interfemoral membrane. _M. suilla_, from Java, the Malay and
neighbouring islands, is a well-known species, and the closely allied
_M. hilgendorfi_ is from Japan. The remaining species are from the
Himalaya, Tibet and Ceylon; and apparently restricted to the
hill-tracts of the countries in which they are found. Next to
_Vespertilio_ the genus _Myotis_ (divisible into several subgenera),
with _i._ 2/3, _p._ 3/3, includes the largest number of species, and
has rather a wider geographical distribution in both hemispheres, one
species being recorded from the Navigator Islands. The species may be
recognized by the peculiar character of the pairs of upper incisors on
each side, the cusps of which diverge from each other, by the large
number of premolars, of which the second upper is always small, and by
the oval elongated ear and narrow tragus. The British _M. bechsteini_
and _M. nattereri_ are examples of this group. _Cerivoula_
(_Kerivoula_), which also has _p._ 3/3, is distinguished by the
parallel upper incisors and the large second upper premolar. There are
numerous African and Indo-Malayan species, of which _C. picta_, from
India and Indo-Malay, is characterized by its brilliant orange fur,
and membranes variegated with orange and black. The genus includes
delicately formed insectivorous, tropical, forest-haunting bats, whose
colouring approximates them to the ripe bananas among which they often
pass the daytime.

Another subgroup, _Minioptereae_, is represented solely by the genus
_Miniopterus_, with _i._ 2/3, _p._ 2/3. The incisors are separated
from one another in front and from the canines; the first phalange of
the middle finger is very short, the crown of the head elevated, and
the tail long. The genus is represented by some half-dozen Old World
species, among which the typical _M. schreibersi_ ranges from Europe,
southern Asia, and Africa to Japan and Australasia.

The last subfamily is that of the _Molossinae_, included by Dobson in
the family _Emballonuridae_. In this group the premaxillae are in
contact or but very slightly separated; the ears are large, with the
tragus small; the dental formula is _i._ 1/1 (1/2 or 1/3), _c._ 1/1,
_p._ 1/2 (2/2), _m._ 3/3; and the fibula is strongly developed. In
their blunt muzzles and many other features these bats undoubtedly
resemble the _Emballonuridae_, from the typical members of which they
differ by the production of the thick tail far beyond the margin of
the interfemoral membrane. They are further characterized by their
broad and stout feet, in which the first, and in most cases also the
fifth, toe is thicker than the rest, and furnished with long bent
hairs; and by the presence of callosities at the base of the thumbs,
and a single pair of large upper incisors occupying the centre of the
space between the canines. The feet are free from the wing-membrane,
which folds up under the fore-arm and legs; the interfemoral membrane
is retractile, being movable backwards and forwards along the tail;
this power of varying its superficial extent confers on these bats
great dexterity in changing the direction of flight. All are able to
walk or crawl well, and spend much of their time on trees. The genus
_Chiromeles_, with _i._ 1/1, _c._ 1/1, _p._ 1/2, _m._ 3/3, the first
hind-toe much larger than and separate from the others, and the widely
sundered ears, is represented by _C. torquata_, a large bat of
peculiar aspect, inhabiting the Indo-Malay countries. This species is
nearly naked, a collar only of thinly spread hairs half surrounding
the neck, and is remarkable for its enormous throat-sac and
nursing-pouches. The former consists of a semicircular fold of skin
forming a pouch round the neck beneath, concealing the orifices of
subcutaneous pectoral glands which discharge an oily fluid of
offensive smell. The nursing-pouch is formed on each side by an
extension of a fold of skin from the side of the body to the inferior
surfaces of the humerus and femur. In the anterior part of this pouch
the teat is placed. The typical genus _Molossus_ (fig. 21) includes
the mastiff-bats, characterized by the dental formula _i._ 1/1 or 1/2,
_p._ 1/2 or 2/2; and by the upper incisors being close together in
front. The genus is restricted to the tropical and subtropical regions
of the New World. _M. obscurus_, a small species common in tropical
America, inhabits the hollow trunks of palms and other trees and the
roofs of houses. The males and females live apart (as is the case in
most if not all bats). In West Africa the mastiff-bats are represented
by _Eomops_, with one species; while _Nyctinomops_ includes a number
of tropical American species more nearly related to the next genus, in
which some of them (fig. 22) were formerly included. The widely spread
_Nyctinomus_, with _i._ 1/3 or 1/2, _p._ 2/2 or 1/2, and the upper
incisors separate in front, includes numerous species inhabiting the
tropical and subtropical parts of both hemispheres. The lips of the
bats of this genus are even more expansible than in _Molossus_, in
many of the species (fig. 22) showing vertical wrinkles. _N.
toeniotis_ (or _cestonii_), one of the largest species, alone extends
into Europe, as far north as Switzerland. _N. johorensis_, from the
Malay Peninsula, is remarkable for the extraordinary form of its ears.
_N. brasiliensis_ is common in tropical America, and extends as far
north as California.

Myzopoda and Mystacops.

Here may be conveniently noticed two very rare and aberrant bats,
_Myzopoda_ (or _Myxopoda_) _aurita_ of Madagascar, and _Mystacops_ (or
_Mystacina_) _tuberculatas_ of New Zealand, the latter of which is
believed to be well-nigh, if not entirely, exterminated. Their
systematic position and affinities are somewhat uncertain; but in the
opinion of O. Thomas[2] the former should typify a separate family,
_Myzopodidae_, in which the latter may also find a place. From all
other bats _Myzopoda_ is distinguished by the presence of a peculiar
mushroom-shaped organ at the base of the large ear, and by the union
of the tragus with the latter, on the inner base of which it forms a
small projection. There are three phalanges in the middle finger; and
the whole inferior surface of the thumb supports a large sessile
horseshoe-shaped adhesive pad, with the circular margin directed
forwards and notched along its edge, while a smaller pad occupies part
of the sole of the hind-foot. Mr Thomas regards this bat as related on
the one hand to the subfamily _Mormopsinae_ of the _Phyllostomatidae_,
and on the other to the _Natalinae_ among the _Vespertilionidae_; both
these groups being regarded by him as of family rank.

_Mystacops_ resembles _Myzopoda_ in having three phalanges to the
middle finger, but differs in that the tail perforates the
interfemoral membrane to appear on its upper surface in the manner
characteristic of the _Emballonuridae_. The greater part of the
wing-membrane is exceedingly thin, but a narrow portion along the
fore-arm, the sides of the body, and the legs, is thick and leathery,
and beneath this thickened portion the wings are folded. Other
peculiarities of structure are found in the form of the claws of the
thumbs and toes, each of which has a small heel projecting from its
concave surface near the base, also in the sole of the foot and
inferior surface of the leg, as shown in fig. 23. The plantar surface,
including the toes, is covered with soft and very lax, deeply wrinkled
skin, and each toe is marked by a central longitudinal groove with
short grooves at right angles to it. The lax wrinkled integument is
continued along the inferior flattened surface of the ankle and leg.
These peculiarities appear to be related to climbing habits in the
species.

_Extinct Bats_.

Palaeontology tells us nothing with regard to the origin of the Chiroptera, all the known fossil species, some of which date back to the Oligocene, being more or less closely allied to existing types, and therefore of comparatively little interest. The origin of the order from primitive insectivorous mammals must have taken place at least as early as the Lower Eocene. It is, however, noteworthy that several of the earlier extinct species appear to be related to the _Rhinolophidae_, which is the most generalized family of the order. Remains of _Pteropodidae_ belonging to existing genera occur in the caves of tropical countries in the eastern hemisphere; and the skeleton of an extinct generic type, _Archaeopteropus_, has been obtained from the Miocene lignite of Italy, which indicates a form to a certain extent transitional in character between typical fruit-bats and the insectivorous bats. The tail, for instance, which in most modern fruit-bats is rudimentary, with only three or four vertebrae, in the fossil has eight complete vertebrae; while the teeth of the extinct form are distinctly cusped. Whether, however, the tail is longer than in the existing _Notopteris_ of Fiji and New Guinea, or whether the molars are more distinctly cusped than is the case with the Solomon Island _Pteropus_ (_Pteralopex_), is not stated. Still, the fact that the Miocene fruit-bat does show certain signs of approximation to the insectivorous (and more generalized) section of the order is of interest. Of the Oligocene forms, _Pseudorhinolophus_ of Europe is apparently a member of the _Rhinolophidae_; but the affinities of _Alastor_ and _Vespertiliavus_, which are likewise European, are more doubtful, although the latter may be related to _Taphozous_. The North American _Vespertilio_ (_Vesperugo_) _anemophilus_ and the European _V. aquensis_ and _V. parisiensis_ are, on the other hand, members of the _Vespertilionidae_, the last being apparently allied to the serotine (_V. serotinus_).

AUTHORITIES.--The above article is based to some extent on the article
in the 9th edition of this work by G.E. Dobson, whose British Museum
"Catalogue" is, however, now obsolete. Professor H. Winge's
"Jordfundae og nulevende Flagermus (Chiroptera)," published in _E.
Mus. Lundi_ (Copenhagen, 1892), contains much valuable information;
and for _Pteropodidae_ Dr P. Matschie's _Megachiroptera_ (Berlin,
1899), should be consulted. For the rest the student must refer to
namerous papers by G.M. Allen, K. Andersen, F.A. Jentink, G.S. Miller,
T.S. Palmer, A.G. Rehn, O. Thomas and others, in various English and
American zoological serials, all of which are quoted in the volumes of
the _Zoological Record_. (R. L.*)

FOOTNOTES:

[1] _Bull. Amer. Mus. Nat. Hist._ vol. xii. (1899).

[2] _Proc. Zool. Soc._ (London, 1904), vol. ii.

CHIRU, a graceful Tibetan antelope (_Pantholops Hodgsoni_), of which the bucks are armed with long, slender and heavily-ridged horns of an altogether peculiar type, while the does are hornless. Possibly this handsome antelope may be the original of the mythical unicorn, a single buck when seen in profile looking exactly as if it had but one long straight horn. Although far from uncommon, chiru are very wary, and consequently difficult to approach. They are generally found in small parties, although occasionally in herds. They inhabit the desolate plateau of Tibet, at elevations of between 13,000 and 18,000 ft., and, like all Tibetan animals, have a firm thick coat, formed in this instance of close woolly hair of a grey fawn-colour. The most peculiar feature about the chiru is, however, its swollen, puffy nose, which is probably connected with breathing a highly rarefied atmosphere. A second antelope inhabiting the same country as the chiru is the goa (_Gazella picticaudata_), a member of the gazelle group characterized by the peculiar form of the horns of the bucks and certain features of coloration, whereby it is markedly distinguished from all its kindred save one or two other central Asian species. The chiru, which belongs to the typical or antilopine section of antelopes, is probably allied to the saiga. (R. L.*)

CHIRURGEON, one whose profession it is to cure disease by operating with the hand. The word in its original form is now obsolete. It derives from the Mid. Eng. _cirurgien_ or _sirurgien_, through the Fr. from the Gr. [Greek: cheirourgos], one who operates with the hand (from [Greek: cheir], hand, [Greek: ergon], work); from the early form is derived the modern word "surgeon." "Chirurgeon" is a 16th century reversion to the Greek origin. (See SURGERY.)

CHISEL (from the O. Fr. _cisel_, modern _ciseau_, Late Lat. _cisellum_, a cutting tool, from _caedere_, to cut), a sharp-edged tool for cutting metal, wood or stone. There are numerous varieties of chisels used in different trades; the carpenter's chisel is wooden-handled with a straight edge, transverse to the axis and bevelled on one side; stone masons' chisels are bevelled on both sides, and others have oblique, concave or convex edges. A chisel with a semicircular blade is called a "gouge." The tool is worked either by hand-pressure or by blows from a hammer or mallet. The "cold chisel" has a steel edge, highly tempered to cut unheated metal. (See TOOL.)

CHISLEHURST, an urban district in the Sevenoaks parliamentary division of Kent, England, 11-1/4 m. S.E. of London, by the South-Eastern & Chatham railway. Pop. (1901) 7429. It is situated 300 ft. above sea-level, on a common of furze and heather in the midst of picturesque country. The church of St Nicholas (Perpendicular with Early English portions, but much restored) has a tomb of the Walsingham family, who had a lease of the manor from Elizabeth; Sir Francis Walsingham, the statesman, being born here in 1536. Another statesman of the same age, Sir Nicholas Bacon, was born here in 1510. Near the church is an ancient cockpit. The mortuary chapel attached to the Roman Catholic church of St Mary was built to receive the body of Napoleon III., who died at Camden Place in 1873; and that of his son was brought hither in 1879. Both were afterwards removed to the memorial chapel at Farnborough in Hampshire. Camden Place was built by William Camden, the antiquary, in 1609, and in 1765 gave the title of Baron Camden to Lord Chancellor Pratt. The house was the residence not only of Napoleon III., but of the empress Eugenie and of the prince imperial, who is commemorated by a memorial cross on Chislehurst Common. The house and grounds are now occupied by a golf club. There are many villa residences in the neighbourhood of Chislehurst.

CHISWICK, an urban district in the Ealing parliamentary division of Middlesex, England, suburban to London, on the Thames, 71/2 m. W. by S. of St Paul's cathedral. Pop. (1901) 29,809. The locality is largely residential, but there are breweries, and the marine engineering works of Messrs Thornycroft on the river. Chiswick House, a seat of the duke of Devonshire, is surrounded by beautiful grounds; here died Fox (1806) and Canning (1827). The gardens near belonged till 1903 to the Royal Horticultural Society. The church of St Nicholas has ancient portions, and in the churchyard is the tomb of William Hogarth the painter, with commemorative lines by David Garrick. Hogarth's house is close at hand. Chiswick Hall, no longer extant, was formerly a country seat for the masters and sanatorium for the scholars of Westminster school. Here in 1811 the Chiswick Press was founded by Charles Whittingham the elder, an eminent printer (d. 1840).

CHITA, a town of east Siberia, capital of Transbaikalia, on the Siberian railway, 500 m. E. of Irkutsk, on the Chita river, half a mile above its confluence with the Ingoda. Pop. (1883) 12,600; (1897) 11,480. The Imperial Russian Geographical Society has a museum here. Several of the palace revolutionaries, known as Decembrists, were banished to this place from St Petersburg in consequence of the conspiracy of December 1825. The inhabitants support themselves by agriculture and by trade in furs, cattle, hides and tallow bought from the Buriats, and in manufactured wares imported from Russia and west Siberia.

CHITALDRUG, a district and town in the native state of Mysore, India. The district has an area of 4022 sq. m. and a population (1901) of 498,795. It is distinguished by its low rainfall and arid soil. It lies within the valley of the Vedavati or Hagari river, mostly dry in the hot season. Several parallel chains of hills, reaching an extreme height of 3800 ft., cross the district; otherwise it is a plain. The chief crops are cotton and flax; the chief manufactures are blankets and cotton cloth. The west of the district is served by the Southern Mahratta railway. The largest town in the district is Davangere (pop. 10,402). The town of CHITALDRUG, which is the district headquarters (pop. 1901, 5792), was formerly a military cantonment, but this was abandoned on account of its unhealthiness. It has massive fortifications erected under Hyder Ali and Tippoo Sahib towards the close of the 18th century; and near it on the west are remains of a city of the 2nd century A.D.

CHITON, the name[1] given to fairly common littoral animals of rather small size which belong to the phylum Mollusca, and, in the possession of a radula in the buccal cavity, resemble more especially the Gastropoda. Their most important characteristic in comparison with the latter is that they are, both in external and internal structure, bilaterally symmetrical. The dorsal integument or mantle bears, not a simple shell, but eight calcareous plates in longitudinal series articulating with each other. The ventral surface forms a flat creeping "foot," and between mantle and foot is a pallial groove in which there is on each side a series of gills. Originally the Chitons were placed with the limpets, _Patella_, in Cuvier's _Cyclobranchia_, an order of the Gastropoda. In 1876 H. von Jhering demonstrated the affinities of _Neomenia_ and _Chaetoderma_, vermiform animals destitute of shell, with the Chitons, and placed them all in a division of worms which he named Amphineura. The discovery by A.A.W. Hubrecht in 1881 of a typical molluscan radula and odontophore in a new genus _Proneomenia_, allied to _Neomenia_, showed that the whole group belonged to the Mollusca. E. Ray Lankester (_Ency. Brit._, 9th ed., 1883) placed them under the name Isopleura as a subclass of Gastropoda. Paul Pelseneer (1906) raised the group to the rank of a class of Mollusca, under von Jhering's name Amphineura.

The Amphineura are divided into two orders: (1) the Polyplacophora, or Chitons; (2) the Aplacophora, or forms without shells, _Neomenia_, _Chaetoderma_ and their allies.

Order I.--POLYPLACOPHORA

A. Dorsal view of _Chiton Wosnessenksii_, Midd., showing the eight
shells. (After Middendorf.)

B. View from the pedal surface of a species of Chiton from the Indian
Ocean, _p_, foot; _o_, mouth (at the other end of the foot is seen the
anus raised on a papilla); _kr_, oral fringe; _br_, the numerous
ctenidia (branchial plumes); spreading beyond these, and all round the
animal, is the mantle-skirt. (After Cuvier.)

C. The same species of Chiton, with the shells removed and the dorsal
integument reflected, _b_, buccal mass; _m_, retractor muscles of the
buccal mass; _ov_, ovary; _od_, oviduct; _i_, coils of intestines;
_ao_, aorta; _c'_, left auricle; _c_, ventricle.]

Each of the eight valves of the shell is made up of two distinct calcareous layers: (a) an outer or upper called the tegmentum, which is visible externally; (b) a deeper layer called articulamentum which is porcellaneous, quite compact, and entirely covered by the tegmentum. In the lower forms the two layers are coextensive and have smooth edges, but in the higher forms the articulamentum projects laterally beyond and beneath the tegmentum into the substance of the mantle. These projections are termed insertion plates; they are usually slit or notched to form teeth, the edges of which may be smooth and sharp, or may be crenulated. The anterior margin of each valve except the first is provided with two projections called sutural laminae which underlie the posterior margin of the preceding valve.

FIG. 3.--Ventral aspect of three species of Polyplacophora showing position of gills.

A. _Lepidopleurus benthus_.

B. _Boreochiton cinereus_.

C. _Schizochiton incisus_. _a_, anus; _f_, foot; _g_, gills; _m_,
mouth; _pa_, mantle; _pa'_, anal lobe of mantle; _ps_, pallial slit;
_te_, pallial tentacles.]

The tegmentum is formed by the fold of mantle covering the edge of the articulamentum, and extends over the latter from the sides. It is the first part of the shell formed in development. The tegmentum is much reduced in _Acanthochiton_, and absent in the adult _Cryptochiton_. The tegmentum is pierced by numerous vertical ramified canals which contain epithelial papillae of the epidermis. These papillae form pallial sense-organs, containing nerve-end bulbs, covered by a dome of cuticle, and innervated from the pallial nerve-cords. They are termed according to their size, micraesthetes and megalaesthetes. In the common species of _Chiton_ and many others of the family _Chitonidae_ the megalaesthetes are developed into definite eyes, the most complicated of which have retina, pigment within the eye, cornea and crystalline lens (intra-pigmental eyes) (fig. 2). The eyes are arranged in rows running diagonally from the median anterior beak of each valve to its lateral borders There may be only one such row on either side, or many rows. In some species the total number present amounts to thousands.

A. Neomenia and Proneomenia.
B. Chaetoderma.
C. Chiton.
_o_, Mouth.
_a_, Anus.
_d_, Alimentary canal.
_l_, Liver (digestive gland).]

_Branchiae._--The series of gills may extend the whole length of the
body in the pallial groove, or may be confined to the posterior end.
Each gill has the structure of a typical molluscan ctenidium,
consisting of an axis bearing an anterior and posterior row of
filaments or lamellae. The gills are thus metamerically repeated;
there may be from four to eighty pairs, but there is often a numerical
asymmetry on the two sides. The largest pair of branchiae is placed
immediately behind the renal openings and corresponds to the single
pair of other molluscs, the organs being repeated anteriorly only
(Metamacrobranchs) or anteriorly and posteriorly (Mesomacrobranchs).

_Intestine._--The digestive tube in the Polyplacophora, which are
herbivorous, is longer than the body, and thrown into a few coils, the
anus being median and posterior. The mouth leads into the buccal
cavity, on the ventral side of which opens the radular caecum. Each
transverse row of teeth of the radula contains 17 teeth, one of which
is median, while the second and the fifth on each side are enlarged.
Two pairs of glands open into the buccal cavity, and at the junction
of pharynx and oesophagus is another pair called the sugar glands. The
stomach is surrounded by the liver or digestive gland, consisting of
two lobes which are symmetrical in the young animals, but in the adult
the right lobe is anterior and smaller.

A, Chaetoderma.
B, Neomenia.
C, Proneomenia.
D, Chiton.
O, Ovary.
P, Pericardium.
N, Nephridium.
u, External aperture of nephridium.
g, External aperture of the genital duct of Chiton.
r, Rectum.
Cl, Cloacal or pallial chamber of Neomeniae and Chaetoderma.
Br, Ctenidia (branchial plumes).]

_Coelom, Gonads and Excretory Organs._--As in other molluscs the
coelom is represented by a large pericardial cavity, situated above
the intestine posteriorly, and a generative sac which is single and
median and situated in front of the pericardium, except in the
_Nuttalochiton hyadesi_, where the gonads are in a similar position,
but are paired. The excretory organs are coelomoducts with an internal
ciliated opening into the pericardium and an opening to the exterior.
Both the openings are close together, the external opening being just
in front of the principal gill near the posterior end of the body. The
renal tube is doubled on itself, its middle part where the bend occurs
being situated more or less anteriorly. The excretory surface is
increased by numerous ramified caeca which extend beneath the body
wall laterally and ventrally, and open into the tube (fig. 6). The
sexes are distinct, and the ovary is frequently greenish in colour,
the testis red. The gonad is transversely wrinkled and lies between
the aorta and the intestine, extending from the pericardium to the
anterior end of the body. A simple gonaduct on each side arises from
the gonad near its posterior end and passes first forwards, then
backwards, and lastly outwards to the external opening in the pallial
groove, anterior to the renal aperture. There may be from one to nine
gills between the genital and renal pores.

_Heart and Vascular System._--The heart is enclosed in the
pericardium, and consists of a median elongated ventricle and a pair of
lateral auricles, so that the structure somewhat resembles that in
the Lamellibranchiata. The openings of the auricles into the
ventricle vary in different forms. In many of the lower forms
(_Lepidopleuridae, Mopalidae, Ischnochitonidae_) the opening on each
side is single and anterior. In the true _Chitonidae_ there are generally
two apertures on each side, and in two species three or four, another
instance of the tendency to metameric repetition in the group.
The auricles are connected with one another posteriorly behind the
ventricle. The ventricle leads into a single anterior median aorta.
As in other molluscs, the arteries do not extend far, but lead into
inter-visceral blood-spaces. The venous blood is conducted from
the tissues to a large sinus on either side above the pallial groove,
and from this sinus passes to the gills by an afferent vessel in each
gill on the internal or pedal margin of the axis. The oxygenated
blood is carried from each gill by an efferent vessel on the external
or pallial side of the axis to another longitudinal vessel which leads
to the auricle on each side.

FIG. 6.--Dissection of the renal organs (nephridia) of _Chiton siculus._

F, Foot.
L, Edge of the mantle not removed in the front part of the specimen.
s.o., Oesophagus.
af, Anus.
gg, Genital duct.
go, External opening of the same.
eg, Stem of the nephridium leading to no, its external aperture.
nk, Reflected portion of the nephridial stem.
ng, Fine caeca of the nephridium, which are seen ramifying
transversely over the whole inner surface of the pedal muscular
mass.]

_Nervous System._--There are no well-marked specialized ganglia in the
central nervous system, nerve-cells being distributed uniformly along
the cords. There are two pairs of longitudinal cords, a pedal pair
situated ventrally and united beneath the intestine by numerous
commissures, and a pallial pair situated laterally and continuous with
one another above the rectum (fig. 7). The four cords are all
connected anteriorly with the cerebral commissure which lies above the
buccal mass anteriorly. From the points where the cords meet the
cerebral commissure, arise on each an anterior labial commissure and a
stomatogastric commissure. The letter bears two ganglion swellings,
the buccal ganglia. The labial commissure gives off a subradular
commissure which also bears two ganglia, these being in close relation
to a special sense-organ called the subradular organ, an epithelial
projection with nerve-endings, lying in front of the radula and
probably gustatory in function. One osphradium or branchial olfactory
organ is usually present on each side, on either side of the anus on
the inner wall of the mantle, near the base of the last gill. In
_Lepidopleuridae_ an osphradium occurs at the base of each gill. The
sense organs of the shell-valves have already been described.

_Development._--The eggs may be laid separately invested by a
chitinous envelope, or as in _Ischnochiton magdalenensis_ they may
form strings containing nearly 200,000 eggs, or the ova may be
retained in the pallial groove and undergo development there, as in
_Chiton polii_ and _Hemiarthrum setulosum_. One species
_Callistochiton viviparus_ is viviparous and its ova develop without a
larval stage in the maternal oviduct. Segmentation is total and at
first regular, and is followed by invagination, the blastopore passing
to the position of the future mouth. By the development of a ciliated
ring just in front of the mouth the embryo becomes a trochosphere. In
the centre of the praeoral lobe is a tuft of cilia. Just behind the
ciliated ring is a pair of larval eyes which disappear in the adult;
these correspond to the cephalic eyes of Lamellibranchs. An ectodemic
invagination forms a large mucous gland on the foot, which is more or
less atrophied in adult life. The gonads originate by proliferation of
the anterior wall of the pericardium. The shell-valves arise as
transverse thickenings of the dorsal cuticle behind the ciliated ring,
the tegmentum being the first part formed.

_Classification_.

FIG. 7.--Diagrams of the nervous system of Amphineura.

A, Proneomenia.
B, Neomenia.
C, Chaetoderma.
D, Chiton.
c, Cerebral ganglia.
s, Sublingual ganglia.
v, Pedal (ventral) nerve-cord.
l, Visceral (lateral) nerve-cord.
pc. Post-anal junction of the visceral nerve-cords.]

FIG. 8.--Anterior part of the nervous system of _Chiton cinereus_,
in more detail.

B, Buccal ganglia (concerned with the odontophore).
C, Cerebral nerve-mass.
P, Pedal ganglion and commencement of pedal nerve-cord.
pl, Visceral nerve-cord. The sublingual ganglia are not lettered.]

Suborder I. EOPLACOPHORA, Pilsbry.--Tegmentum coextensive with
articulamentum, or the latter projecting in smooth unslit plates.

Fam. 1. _Lepidopleuridae._--Terminal margins of end valves never
elevated; form oval or oblong. _Lepidopleurus cancellatus_, Sow.
North Atlantic and Mediterranean; various abyssal species. _Hanleya
hanleyi_, Bean, north Atlantic. _Hemiarthrum Microplax_. The extinct
_Gryptochitonidae_, Pilsbry, with other Palaeozoic genera, narrow
and elongated in form with terminal margins of end valves elevated,
belong to this group.

Suborder II. MESOPLACOPHORA, Pilsbry.--Insertion plates well developed
and slit.

Fam. 2. _Ischnochitonidae._--All the valves with slits, and the
inner layer well covered by the outer.

Subfam. 1. _Ischnochitoninae._--No shell-eyes: sutural laminae
separated; slits in the valves 1-7 do not correspond with the ribs
of the tegmentum. _Ischnochiton, Trachydermon, Chaetopleura,
Stenoplax, Stenoradsia_.

Subfam. 2. _Callochitoninae._ With shell-eyes and united sutural
laminae. _Callochiton laevis_, North Atlantic and Mediterranean.

Subfam. 3. _Callistoplacinae._ No shell-eyes, slits in the valves
1-7 corresponding with the ribs of the tegmentum. _Callistochiton_
(viviparous). _Nuttalochiton._

Fam. 3. _Mopaliidae._ Each intermediate valve with a single slit;
girdle hairy. _Mopalia, Placiphorella, Plaxiphora, Placophoropsis._