Chapter XI

FOSSIL TRILOBITES, CRUSTACEA AND INSECTS.

=Arthropods and their Structure.--=

The above-named fossil groups are included by zoologists in the sub-kingdom Arthropoda ("joint-footed animals"). The Arthropods possess a body and limbs composed of a number of jointed segments covered externally with a hard, shelly material and separated by a softer, flexible skin. They have no internal skeleton, and therefore the only portion which can be preserved in the fossil state is the harder part of the outer covering. Under exceptional conditions of fossilisation, however, even frail insects such as ants, wasps and dragon-flies are sometimes found more or less wholly preserved and showing their original minute structure.

=Subdivisions of Arthropoda.--=

The principal representatives of the group of the Arthropods which are found as fossils include the Trilobites; various Crustacea proper, as Crabs, Lobsters, Shrimps, Pod-shrimps and Water-fleas; the Insects; and occasionally Spiders and Scorpions (Arachnida). The King-crabs and Eurypterids (as the extinct _Pterygotus_) form a separate sub-class, the Merostomata, which are placed by some authors in the group of Spiders and Scorpions: their remains date back to the time when the older Palaeozoic strata were deposited.

=Crustacea, an Archaic Group.--=

A typical division of the Arthropod group, and one which was well represented from the earliest period up to the present day, is the _CRUSTACEA_. As the name denotes, these animals are generally invested with a strong shelly covering or "crust," usually of horny or chitinous material, which in some forms is strengthened by deposits of phosphate of lime. Of the horny condition of the shell the groups of the bivalved Crustacea (Ostracoda) and the "water-fleas" (Entomostraca) supply notable instances; whilst the limy-structured shell is seen in the common crab. Some authorities separate the great extinct group of the Trilobites from the rest of the Crustacea; but it will here be convenient, in a preliminary study, to consider them together.

=Development of Crustacea.--=

The development of the lower forms of the Crustacea is interesting, from the fact that the young usually escapes from the egg in a larval state known as a "nauplius." In this stage there are no segments to the body, and but a solitary median eye, such as may be seen in the common water-flea known to microscopists as _Cyclops_. The three pairs of appendages seen in this larval crustacean represent the two pairs of antennae and the jaws or mandibles of the full-grown form.

Among the higher Crustacea, however, there is no larval form; the young escaping from the egg in a more or less highly developed condition resembling the adult. The group of the Crabs, Lobsters and Shrimps (or Decapoda, _i.e._, having ten ambulatory feet) exhibit a larval stage in which the young form ("zoea") has a segmented abdomen and seven pairs of appendages.

=Trilobites.--=

The first group of arthropods here described is that of the _TRILOBITES_. These were so named on account of the three-lobed form of the body. This particular feature distinguishes them from the Crustacea proper; which includes the Phyllopods (with leaf-like limbs), as the freshwater _Estheria_, the Ostracoda or Bivalved Water-fleas, the Barnacles or Cirripedia and the Higher Crustacea (Malacostraca), including Shrimps, Crabs, and Lobsters, of which the oldest representatives are the Pod-shrimps (Phyllocarida).

=Habits of Trilobites.--=

The remains of these primitive but often strikingly ornamented crustacean-like animals, the trilobites, are found in comparative abundance in the limestones, mudstones, and even the sandstones of the older sedimentary rocks of Australasia. They were amongst the most prolific types of animal life existing in the seas of Palaeozoic times, and are especially characteristic of Cambrian, Ordovician and Silurian rocks. Trilobites, as a group, seem to have adapted themselves to almost all conditions of marine life: some are found in the hardened black mud of shallow waters, whilst others are to be looked for in the limestones and excessively fine sediments of deeper waters. In all probability certain of these forms crawled over the soft, oozy sea-bed in order to obtain their food, and consequently their remains in the stratified rocks would be restricted to the fine black shales; whilst the freely swimming forms could change their habitat at will, and would be found alike in sandy or clayey deposits. As some indication of their varied habits, the eyes of trilobites differ greatly in size. They are always compound like the eye of the house-fly, though of a semi-lunar shape. In some forms the eyes are very small or even absent, whilst in others they are exceedingly large and prominent. This latter feature probably indicates their frequenting moderately deep water.

(Dalmanites meridianus, Eth. fil. and Mitch, sp.)

To show the sutures or joints, and the structure of the back of the carapace.

About 2/3 natural size.
]

=Structure of Trilobites.--=

The complete structure and zoological relationship of the trilobites has always been open to some doubt. As regards the former, within recent years exceptionally well-preserved specimens from the Utica Slates and the Cincinnati Limestone of Ohio, rocks of Ordovician age, have been discovered and dissected, whereby our knowledge of the organisation of this group is greatly advanced. These remarkable fossil remains show that the Trilobites bore on their under surface a number of appendages, one pair to each segment, except that of the anal. The front pair is whip-like and served as antennae; the others are branched, the forward portion being a crawling limb, and the hinder, which was fringed with bristles or thin plates, may have served either for swimming or breathing. At the base of the four pairs of appendages attached to the head there was an arrangement for biting the food, from whence it was passed to the mouth. Taking one of the commonest Australasian trilobites, _Dalmanites meridianus_, for an example of general structure, and looking at the back of the shell or upper surface, we see the trilobate (three-lobed) form well defined (Fig. 107). The central ridge is termed the axis, and on either side of this are arranged the pleural lobes, each well marked transverse division of which, in the central or thoracic region, being a pleuron or rib. The whole body is divided into three more or less distinct portions,--the head-shield or cephalon, the thorax, and the tail-shield or pygidium. The central area of the head-shield is called the glabella or cranidium, against which, on either side, are placed the free cheeks carrying the compound sessile eyes when present. The appendages of the head are pediform or leglike, arranged in five pairs, and biramous or forked, excepting the antennae, which are simple and used as sensory organs. In front of the mouth is the hypostoma or forelip, and behind it is the metastoma or hind-lip. The segments of the head-shield are most closely united, and in all the trilobites are of the same number. Those of the thorax have flexible joints and are variable in number. The segments of the abdomen are fused together and form a caudal shield or pygidium.

The larval stage of the trilobite was a protonauplian form (that is more primitive than the nauplius), the protoaspis; the adult stage, being attained by the addition of segments at the successive moults.

The earliest known trilobites in Australia are some Cambrian species from South Australia, Western Australia, Victoria, and Tasmania.

=Lower Cambrian Trilobites.--=

A--Ptychoparia howchini, Eth. fil. L. Cambrian. South Australia

B--Dolichometopus tatei, H. Woodw. L. Cambrian. South Australia

C--Agnostus australiensis, Chapm. Up. Cambrian. Victoria

D--Ptychoparia thielei, Chapm. Up. Cambrian. Victoria

E--Dikellocephalus florentinensis, Eth. fil. L. Cambrian. Tasmania

]

In the Lower Cambrian Limestone of Yorke Peninsula, South Australia, the following trilobites occur:--a species doubtfully referred to _Olenellus_ (? _O. pritchardi_); _Ptychoparia howchini_ (Fig. 108 A); _P. australis_; _Dolichometopus tatei_ (Fig. 108 B); and _Microdiscus subsagittatus_. The Cambrian of the Northern Territory contains _Olenellus brownii_. In Western Australia _Olenellus forresti_ is found in similar beds.

=Upper Cambrian Trilobites.--=

The Dolodrook Limestone (Upper Cambrian) of Gippsland, Victoria, contains the remains of the primitive little trilobite _Agnostus_ (_A. australiensis_, Fig. 108 C); _Crepicephalus_ (_C. etheridgei_); and _Ptychoparia_ (_P. thielei_ (Fig. 108 D) and _P. minima_). The Upper Cambrian sandstones of Caroline Creek, Tasmania, contain _Dikellocephalus_ (_D. tasmanicus_); a species of _Asaphus_ and _Ptychoparia_ (_P. stephensi_). Beds of the same age in the Florentine Valley, Tasmania, have yielded _Dikellocephalus_ (_D. florentinensis_, Fig. 108 E).

=Ordovician Trilobites.--=

Trilobites of Lower Ordovician age or even older, are found in the Knowsley beds near Heathcote in Victoria. They are referred to two genera, _Dinesus_ and _Notasaphus_. Both forms belong to the ancient family of the Asaphidae. Associated with these trilobites are some doubtful species of sea-weed, spicules of siliceous sponges, traces of threadlike hydrozoa, some fragments of graptolites allied to _Bryograptus_, and several brachiopods. At the Lyndhurst Gold-fields, near Mandurama, New South Wales, trilobites related to the genus _Shumardia_ have been found associated with brachiopods (lamp-shells), pteropods (sea-butterflies), and graptolites (hydrozoa) of an Upper Ordovician facies.

The limestone beds at Laurie's Creek and other localities in Central Australia contain remains of _Asaphus illarensis_, _A. howchini_ and _A. lissopelta_; whilst in the limestone and quartzite of Middle Valley, Tempe Downs, _A. thorntoni_ also occurs.

=Silurian Trilobites.--=

A--Ampyx parvulus, Forbes, var. jikaensis, Chapm. Silurian (Melb.)
Victoria

B--Cypaspis spryi, Gregory. Silurian (Melb.) Victoria

C--Homalonotus harrisoni, McCoy. Silurian (Melb.) Victoria

D--Phacops latigenalis, Eth. fil. and Mitch. Silurian. N.S. Wales

]

Trilobites are well-known fossils in the Australasian Silurian strata. As they occur rather abundantly along with other fossils in rocks of this age they are extremely useful aids in separating the system into the different beds or zones. In Victoria the Silurian is divisible into two sets of beds: an older, or Melbournian stage (the bed-rock of Melbourne) and a younger, Yeringian (Lilydale series). Trilobites of Melbournian age are found to belong to the genera _Ampyx_, _Illaenus_, _Proetus_, _Cyphaspis_, _Encrinurus (Cromus)_ and _Homalonotus_. The commonest species are _Cyphaspis spryi_ (Fig. 109 B), and _Encrinurus (Cromus) spryi_ from the South Yarra mudstones; and _Ampyx parvulus_, var. _jikaensis_ (Fig. 109 A), and _Homalonotus harrisoni_ (Fig. 109 C), from the sandstone of Moonee Ponds Creek.

The handsome _Dalmanites meridianus_ and _Homalonotus vomer_ occur at Wandong in what appear to be passage beds between the Melbournian and Yeringian.

The Yeringian of Victoria is far richer in trilobites than the preceding series, and includes the genera _Proetus_, _Cyphaspis_, _Bronteus_, _Lichas_, _Odontopleura_, _Encrinurus_, _Calymene_, _Homalonotus_, _Cheirurus_, and _Phacops_. The rocks in this division occur as mudstones, limestones, and occasionally sandstones and conglomerates. The mudstones, however, prevail, and these pass insensibly into impure limestones of a blue-black colour, weathering to brown, as at Seville; the change of structure indicating less turbid water. At Lilydale, and on the Thomson River, as well as at Loyola and Waratah Bay, almost pure limestone occurs, which represents clear water conditions, not necessarily deep; there, however, trilobites are scarce, and the prevailing fauna is that of an ancient coral reef. Some described Yeringian species are _Lichas australis_ (Fig. 110 A), _Odontopleura jenkinsi_ (Fig. 110 B) (found also in New South Wales), _Encrinurus punctatus_ (Fig. 110 C), _Calymene tuberculosa_, _Bronteus enormis_, _Phacops sweeti_, and _P. serratus_ (Fig. 110 E). In _Calymene_ ("covered up") the joints of the thorax are facetted at the angles, so that each pleuron could work over that immediately behind; in consequence of this it could roll itself up like a woodlouse or slater, hence the name of the genus. This trilobite also occurs in England, and is there known amongst the quarry men and fossil collectors as the "Dudley Locust." Perhaps the most characteristic and common trilobite of the Yeringian series in Victoria is _Phacops sweeti_ (Fig. 110 D), formerly identified with Barrande's _P. fecundus_, from which it differs in the longer and larger eye with more numerous lenses. It is found in Victoria in the Upper Yarra district near the junction of the Woori Yallock and the Yarra Rivers; north-west of Lilydale; near Seville; at Loyola near Mansfield; and at Fraser's Creek near Springfield, Kilmore.

A--Lichas australis, McCoy. Silurian (Yeringian). Victoria

B--Odontopleura jenkinsi. Eth. fil. and Mitch. Silurian. N.S. Wales

C--Encrinurus punctatus, Brunnich sp. Silurian. N.S. Wales.

D--Phacops sweeti, Eth. fil. and Mitch. Silurian. N.S. Wales

E--Phacops serratus, Foerste. Silurian. N.S. Wales

]

In New South Wales trilobites are abundant in the Yass district, amongst other localities, where the upper beds, corresponding to the Yeringian of Victoria, are well developed. _Dalmanites meridianus_ is common to the Silurian of New South Wales, Victoria, and Tasmania. In Victoria this handsome species is found in the hard, brown, sandy mudstone of Broadhurst's and Kilmore Creeks, and, as previously noted, in the hard, blue mudstone of Wandong. At the latter locality specimens may be found in the railway ballast quarry, where they are known to the workmen as "fossil butterflies." The species also occurs at the famous fossil locality of Hatton's Corner, Yass; at Bowning; and at Limestone Creek, all in New South Wales. Other trilobites occurring in the Silurian of New South Wales are _Odontopleura jenkinsi_, _O. bowningensis_, _Cheirurus insignis_ and _Phacops latigenalis_ (Fig. 109 D).

In the Wangapeka series of New Zealand the calcareous shales and limestones of the upper division contain _Calymene blumenbachii_, _Homalonotus knightii_ and _H. expansus_.

=Devonian Trilobites.--=

Trilobites suddenly became rare in the Australian Devonian. The only known examples of trilobite remains belong to a species of _Cheirurus_ occasionally found in the Middle Devonian limestone of Buchan, Victoria; and a species of _Proetus_ in the Devonian of Barker Gorge, Napier Range, West Australia.

=Carbopermian Trilobites.--=

Trilobites of Carbopermian age are found in New South Wales, Queensland, and Western Australia. All the genera belong to the family Proetidae. The genera _Phillipsia_ (_P. seminifera_, Fig. 111 A), _Griffithides_ (_G. eichwaldi_, Fig. 111 B), and _Brachymetopus_ (_B. strzelecki_, Fig. 111 C) occur in New South Wales. _Griffithides eichwaldi_ is also found in Queensland. Other Queensland species are _Phillipsia woodwardi_, _P. seminifera_ var. _australasica_ and _P. dubia_. _Phillipsia grandis_ is found in the Carbopermian of the Gascoyne River, Western Australia.

A--Phillipsia seminifera, Phillips. Carboniferous. N.S. Wales

B--Griffithides eichwaldi, Waldheim. Carboniferous. N.S. Wales

C--Brachymetopus strzelecki, McCoy. Carboniferous. N.S. Wales

D--Estheria coghlani, Cox. Triassic. N.S. Wales

]

=Phyllopoda in Carboniferous, Triassic and Jurassic.=

The _PHYLLOPODA_, which belong to the Crustacea in the strict sense of the term, comprise the Estheriidae and Cladocera (water-fleas). The former group is represented by _Leaia mitchelli_, which is found in the Upper Carboniferous or Carbopermian of the Newcastle District, New South Wales. In the still later Hawkesbury series (Triassic) of New South Wales, _Estheria coghlani_ (Fig. 111 D) occurs. This species is a minute form, the carapace measuring from 1.25mm. to 2mm. in the longer diameter of the shell. In the upper part of the Wairoa Series (Triassic) of Nelson, New Zealand, there is found another species of _Estheria_, identified with a European form _E. minuta_. _Estheria mangaliensis_ is another form occurring in the Jurassic (Ipswich series) of Queensland. At the present day these little _Estheriae_ sometimes swarm in countless numbers in freshwater lakes or salt marshes.

=Ostracoda: Their Structure.--=

Passing on to the next group, the bivalved _OSTRACODA_, we note that these have existed from the earliest geological periods to the present day. They are usually of minute size, commonly about the sixteenth of an inch in length, although some attained a length of nearly one inch (_Leperditia_). Their bodies are indistinctly segmented, and are enclosed within a horny or calcareous shell. This shell consists of two valves which are joined along the back by a ligament or hinge, the ends and ventral edge remaining quite free. The pairs of appendages present are the antennae (2), mandibles (1), maxillae (2), and thoracic feet (2). The only portion found in the fossil state is the bivalved carapace, the two valves being frequently met with still united, especially when these tiny animals have settled down quietly on the sea-bed and have been quickly covered with sediment.

=Features of the Ostracod Carapace.--=

Since the body parts of the ostracod are wanting in the fossil examples, the generic determination is attended with some difficulty, especially in regard to the smooth or bean-shaped forms. The chief distinctive characters to note are, the contour of the carapace seen in three directions (top, side and end views), the structure of the hinge, and the position and figure of the muscle-spots or points of adhesion of the muscular bands which hold or relax the two valves. The valves in certain genera fit closely upon one another. In others, one overlaps the other, the larger being sometimes the right (as in _Leperditia_), sometimes the left (as in _Leperditella_). The hinge-line is often simple or flange-like, or it may consist of a groove and corresponding bar, or there may be a series of teeth and sockets. Lateral eye-tubercles are sometimes seen on the surface of the valve, whilst in the animal there was also a small eye.

=Habits of Ostracoda.--=

Ostracoda swarmed in many of the streams, lakes and seas of past geological times, and they still exist in vast numbers under similar conditions. Like some other minute forms of life, they played a most important part in building up the rock formations of the sedimentary series of the earth's crust; and by the decomposition of the organism itself they are of real economic value, seeing that in some cases their decay resulted in the subsequent production of oil or kerosene shales and bituminous limestones. The Carboniferous oil shales in the Lothians of Scotland, for example, are crowded with the carapaces of Ostracoda associated with the remains of fishes.

=Cambrian Ostracoda.--=

Some undescribed forms of the genus _Leperditia_ occur in the hard, sub-crystalline Cambrian Limestone of Curramulka, South Australia.

=Silurian Ostracoda.--=

In Victoria and New South Wales the oldest rocks from which we have obtained the remains of Ostracoda up to the present, are the uppermost Silurians, in which series they occur both in the limestone and the mudstone. In Victoria their bivalved carapaces are more often found in the limestone; but one genus, _Beyrichia_, is also met with in abundance in the mudstone. These mudstones, by the way, must have originally contained a large percentage of carbonate of lime, since the casts of the shells of mollusca are often excessively abundant in the rock, and the mudstone is cavernous, resembling an impure, decalcified limestone. These Yeringian mudstones of Victoria seem, therefore, to be the equivalent of the calcareous shales met with in the Wenlock and Gotland Series in Europe; a view entirely in accordance with the character of the remainder of the fauna. One of the commonest of the Silurian ostracods is _Beyrichia kloedeni_, a form having an extensive distribution in Europe. It occurs in the Silurian mudstone of the Upper Yarra District. Other species of the same genus are _B. wooriyallockensis_ (Fig. 112 A), distinguished from the former by differences in the shape of the lobes and its longer valves; also a form with narrow lobes, _B. kilmoriensis_; and the ornate _B. maccoyiana_, var. _australis_. Of the smooth-valved forms, mention may be made of _Bythocypris hollii_, _B. caudalis_ (Fig. 112 D), and the striking form, _Macrocypris flexuosa_. Regarding the group of the _Primitiae_, of which as many as thirteen species and varieties have been described from the Lilydale Limestone, we may mention as common forms _P. reticristata_ (Fig. 112 E) and _P. punctata_. This genus is distinguished by the bean-shaped or purse-shaped carapace, with its well developed marginal flange and mid-dorsal pit. Other genera which occur in our Silurians and are of great interest on account of their distribution elsewhere. are _Isochilina_, _Aparchites_, _Xestoleberis_, _Aechmina_, and _Argilloecia_.

A--Beyrichia wooriyallockensis, Chapm. Silurian (Yer.) Victoria

B--Xestoleberis lilydalensis, Chapm. Silurian (Yer.) Victoria

C--Argilloecia acuta, Jones and Kirkby. Silurian (Yer.) Victoria

D--Bythocypris caudalis, Jones. Silurian (Yer.) Victoria

E--Primitia reticristata, Jones. Silurian (Yer.) Victoria

]

The largest ostracod yet described from Australia, measuring more than a quarter of an inch in length, occurs in the Upper Silurian of Cliftonwood, near Yass, New South Wales. It belongs to the genus _Leperditia_ (_L. shearsbii_), and is closely related to _L. marginata_, Keyserling sp.; which occurs in strata of similar age in the Swedish and Russian Baltic area. A limestone at Fifield, New South Wales, probably of Silurian age, contains _Primitia_, _Kloedenia_, and _Beyrichia_.

=Devonian Ostracoda.--=

The little _Primitia cuneus_ (Fig. 113 A) with a bean-shaped carapace and median pit or depression occurs somewhat frequently in the Middle Devonian Limestone of Buchan, Victoria. Another species, _Primitia yassensis_, is found in the shaly rock of Narrengullen Greek, New South Wales. It is probable that many other species of the group of the ostracoda remain to be described from Australian Devonian rocks.

=Carboniferous Ostracoda.--=

In Queensland a conspicuous little ostracod is _Beyrichia varicosa_ from the Star Beds of Corner Creek.

=Carbopermian Ostracoda.--=

In the Carbopermian of Cessnock, New South Wales, _Primitia dunii_ occurs; and in that of Farley is found _Jonesina etheridgei_. From both these localities _Leperditia prominens_ was also obtained. Another species from New South Wales is _Entomis jonesi_ (Fig. 113 B), described from the Muree Sandstone by de Koninck.

A--Primitia cuneus, Chapm. Mid. Devonian. Victoria

B--Entomis jonesi, de Kon. Carboniferous. New South Wales

C--Synaphe mesozoica, Chapm. sp. Triassic. New South Wales

D--Cythere lobulata, Chapm. Jurassic. West Australia

E--Paradoxorhyncha foveolata, Chapm. Jurassic. West Australia

F--Loxoconcha jurassica, Chapm. Jurassic. West Australia

G--Cytheropteron australiense, Chapm. Jurassic. West Australia

]

=Triassic Ostracoda.--=

The Triassic (Wiannamatta Shales) of Grose Vale, New South Wales has afforded a few specimens of ostracoda belonging to _Synaphe_ (_S. mesozoica_, Fig. 113 C), _? Darwinula_, and _? Cytheridea_.

=Jurassic Ostracoda.--=

The marine Jurassic strata of Western Australia at Geraldton, have yielded a small but interesting series of ostracoda, largely of modern generic types. The genera, which were found in a rubbly _Trigonia_-Limestone, are _Cythere_, _Paradoxorhyncha_, _Loxoconcha_, and _Cytheropteron_.

A--Bairdia amygdaloides, G. S. Brady. Balcombian. Victoria

B--Cythere clavigera, G. S. Brady. Balcombian. Victoria

C--Cythere scabrocuneata, G. S. Brady. Balcombian. Victoria

D--Cytherella punctata, G. S. Brady. Balcombian. Victoria

]

=Cainozoic Ostracoda.--=

The fossiliferous clays and calcareous sands of the southern Australian Cainozoic beds often contain abundant remains of ostracoda. The moderately shallow seas in which the fossiliferous clays, such as those of Balcombe's Bay, were laid down, teemed with these minute bivalved Crustacea. All the forms found in these beds are microscopic. They either belong to living species, or to species closely allied to existing forms. Some of the more prominent of the Balcombian species are _Cythere senticosa_, a form which is now found living at Tenedos, and _C. clavigera_ (Fig. 114 B), with the young form sometimes referred to as _C. militaris_, a species which may still be dredged alive in Hobson's Bay. Other genera common in these clays are _Bairdia_, with its broad, pear-shaped carapace, represented by the still living _B. amygdaloides_ (Fig. 114 A). _Cytherella_, with its compressed, subquadrate carapace, as seen in _C. punctata_ (Fig. 114 D), a species having an elaborate series of muscle-spots, and which, like the previous species, is found living in Australian seas; and _Macrocypris_, with its slender, pointed, pear-shaped outline.

=Cirripedia: Their Habits and Structure.--=

_CIRRIPEDIA OR BARNACLES._--These curious modifications of the higher group of Crustacea (Eucrustacea) date back to Ordovician times. They appear to have tried every possible condition of existence; and although they are mostly of shallow water habits, some are found at the great depth of 2,000 fathoms (over two miles). Those which secrete lime or have calcareous shells, attach themselves to stones, pieces of wood, shell-fish, crabs, corals and sea-weeds. Others are found embedded in the thick skin of whales and dolphins, or in cavities which they have bored in corals or shells of molluscs. Some are found parasitic in the stomachs of crabs and lobsters, or within other cirripedes. They begin life, after escaping from the egg, as a free-swimming, unsegmented larva ("nauplius" stage), and before settling down, pass through the free-swimming, segmented "cypris" stage, which represents the pupa condition, and in which state they explore their surroundings in search of a suitable resting place for their final change and fixed condition. Just before this occurs, glands are developed in the pupa barnacle, which open into the suckers of the first pair of appendages or antennae. When a suitable place for fixation has been found, these glands pour out a secretion which is not dissolved by water, and thus the barnacle is fixed head downwards to its permanent position. The compound eyes of the "cypris" stage disappear, and henceforth the barnacle is blind. The characteristic plates covering the barnacle are now developed, and the six pairs of swimming feet become the cirri or plumes, with which the barnacle, by incessant waving, procures its food. In short, as remarked by one authority, it is a crustacean "fixed by its head, and kicking the food into its mouth with its legs."

Cirripedes may be roughly divided into two groups, the Acorn Barnacles and the Goose Barnacles. Although dissimilar in general appearance, they pass through identical stages, and are closely related in most of their essential characters. The latter forms are affixed by a chitinous stalk or peduncle, whilst the acorn barnacles are more or less conical and affixed by the base.

=Silurian Cirripedes.--=

The stalked barnacles are probably the oldest group, being found as far back as the Ordovician period. In Australia the genus _Turrilepas_ occurs in Silurian rocks, _T. mitchelli_ (Fig. 115 A) being found at Bowning in the Yass District of New South Wales. The isolated plume-like plates of _T. yeringiae_ (Fig. 115 B) are not uncommon in the olive mudstone of the Lilydale District in Victoria.

A--Turrilepas mitchelli, Eth. fil. Silurian. New South Wales

B--Turrilepas yeringiae, Chapm. Silurian. Victoria

C--(?) Pollicipes aucklandicus, Hector sp. Cainozoic (Oamaru series).
New Zealand

]

A--Lepas anatifera, L. Common Goose Barnacle. Living

B--Lepas pritchardi, Hall. Cainozoic. Victoria

]

=Cainozoic Lepadidae.--=

The genus _Lepas_ (the modern goose barnacles) is represented by isolated plates in the Cainozoic (Janjukian) limestones and marls of Waurn Ponds, and Torquay near Geelong: it also occurs in a stratum of about the same age, the nodule bed, at Muddy Creek, near Hamilton, Victoria (_L. pritchardi_, Fig. 116). In New Zealand the gigantic cirripede, _?Pollicipes aucklandicus_ (Fig. 115 C), occurs in the Motutapu beds.

=Cainozoic Balanidae.--=

The Acorn Barnacles are represented in our Cainozoic shell marls and clays by a species of _Balanus_ from the Janjukian of Torquay; whilst two species of the genus occur in the Kalimnan beds at Beaumaris, Port Phillip, in similar beds in the Hamilton District, and at the Gippsland Lakes.

=Phyllocarida: Their Structure.--=

A large and important group of the higher Crustacea, but confined to the older rocks of Victoria, is the order _PHYLLOCARIDA_. This seems to form a link between the Entomostraca, including the bivalved Ostracoda and the well-known group of the lobsters, shrimps and crabs. The body of these phyllocarids consists of five segments to the head, eight to the thorax, and from two to eight to the abdomen. The portion usually preserved in this group is the carapace, which covers the head and thorax, and although often in one piece, is sometimes hinged, or otherwise articulated along the back. In front of the carapace there is a moveable plate, the rostrum or beak (Fig. 117). There are two pairs of antennae to the head, and the animal is provided with a pair of stalked compound eyes. The thoracic segments are furnished with soft leaf-like legs as in the Phyllopods. The abdomen is formed of ring-like segments, and generally terminates in a sharp tail-piece or telson, often furnished with lateral spines. In many respects the ancient phyllocarids correspond with the living genus _Nebalia_, which is found inhabiting the shallow waters of the Mediterranean and elsewhere.

Silurian. Lanarkshire.

(_After H. Woodward_)
]

A--Rhinopterocaris maccoyi, Eth. fil. sp. L. Ordovician. Victoria

B--Caryocaris angusta, Chapm. L. Ordovician. Victoria

C--Saccocaris tetragona, Chapm. L. Ordovician. Victoria

]

A--Ceratiocaris pritchardi, Chapm. Silurian. Victoria

B--Ceratiocaris cf. murchisoni, Agassiz sp. Silurian. Victoria

C--Ceratiocaris pinguis, Chapm. Silurian. Victoria

]

=Ordovician Phyllocarids.--=

Phyllocarids of the Lower Ordovician slates are referred to the genera _Rhinopterocaris_, _Caryocaris_, _Saccocaris_ and _Hymenocaris_. The first-named is the commonest type; and is found in slates of the Lancefield, Bendigo and Castlemaine Series at the localities named, as well as at Dromana. _Rhinopterocaris_ (Fig. 118 A) is readily distinguished by its long--ovate outline, and this, together with its wrinkled chitinous appearance makes it resemble the wing of a dipterous insect. _Caryocaris_ (Fig. 118 B) is a smaller and narrower form which occurs in the Victorian Lower Ordovician slates, as well as in ice-borne blocks derived from the Ordovician, at Wynyard, in N.W. Tasmania.

=Silurian Phyllocarids.--=

The chief type of Phyllocarid in the Silurian is _Ceratiocaris_ (Fig. 119). The carapace is typically ovate, straight on one edge, the dorsal, and convexly curved on the other, the ventral. They resemble bean-pods in outline, hence the name "pod-shrimps." Several species are known from the Victorian shales, mudstones, and sandstones; the forms found in Australia if complete would seldom attain five inches in length, whilst some British species are known to reach the exceptional length of two feet. The long, grooved and jointed telson is not uncommon in the sandstones of Melbourne and Kilmore. Other genera described from Victoria are _Aptychopsis_ and _Dithyrocaris_.

=Lower Cretaceous Crab.--=

The earliest example of the _DECAPODA_ in the Australian rocks, so far recorded, is the Lower Cretaceous _Prosopon etheridgei_ (Fig. 120 A) from Queensland, which has affinities with some Jurassic and Neocomian crabs found in Europe. Other crustacean remains of less decipherable nature occur in this same deposit.

A--Prosopon etheridgei, H. Woodw. L. Cretaceous. Queensland

B--Ommatocarcinus corioensis, Cressw. sp. Cainozoic (Jan.) Vic.

C--Harpactocarcinus tumidus, H. Woodw. Cainozoic (Oamaru). New Zealand

D--Aeschna flindersensis, H. Woodw. L. Cretaceous. Queensland

E--Ephemera culleni, Eth. fil. and Olliff. Cainozoic (Deep Leads). New
South Wales

]

=Cainozoic Crabs.--=

Of the Cainozoic decapod Crustacea there is a Victorian species of a stalk-eyed crab, _Ommatocarcinus corioensis_ (Fig. 120 B), found in the marls of Curlewis and Port Campbell, and probably of Janjukian age. Various portions of similar Crustacea, consisting of claws and fragmentary carapaces, are found from time to time in the Victorian clays and limestones of Balcombian and Janjukian ages, but they are insufficient for identification. A carapace of one of the Oxystomata (with rounded cephalo-thorax and non-salient frontal region) has occurred in the Kalimnan marl of the Beaumaris Cliffs, Port Phillip. It is closely allied to a crab now found in Hobson's Bay and generally along the Victorian coast.

Remains of a shore-crab (Fam. Cancridae) are found at three localities, in the Oamaru Series, in New Zealand; near Brighton, in Nelson and at Wharekuri in the Waitaki Valley. It has been described under the name of _Harpactocarcinus tumidus_ (Fig. 120 C), a genus of the Cyclometopa or "bow crabs."

=Pleistocene Lobster.--=

Numerous remains of a lobster, _Thalassina emerii_ (see _antea_, Fig. 20), supposed to be of Pleistocene age, occur in nodules found on Queensland and North Australian (Port Darwin) beaches.

=Eurypterids in the Silurian.--=

The order _EURYPTERIDA_ comprises an extinct group of Crustacea closely allied to the modern King-crab (_Limulus_). The body was covered with a thin chitinous skeleton, ornamented with regular scale-like markings. This group is represented in Victorian rocks by the remains of _Pterygotus_ ("Sea-scorpions"), animals which often attained a length of six feet. _Pterygotus_ (see Fig. 121 A) had the fore part of the body fused, forming the cephalo-thorax, which was furnished with anterior, marginal facetted eyes and central ocelli or smaller simple ones. To the ventral surface of the body were attached six pairs of appendages. The first pair are modified antennae with pincer-like terminations, used for prehensile purposes. Then come four pairs of slender walking feet. The sixth pair of appendages is in the form of powerful swimming feet or paddles, at the bases of which are the comb-like jaws. The abdomen consists of thirteen joints, the last of which, the telson, is spatulate and posteriorly pointed. Fragments of a tolerably large species of _Pterygotus_ occur in the Silurian shales of South Yarra, Melbourne, Victoria. It was probably about 18 inches in length when complete. Of this form, known as _P. australis_ (Fig. 121 B), portions of the chelate (clawed) appendages, and parts of the abdominal segments have been found from time to time, but no complete fossil has yet been discovered.

A--Pterygotus osiliensis, Schmidt. I. of Oesel. (_After Schmidt_)

B--Pterygotus australis, McCoy. Part of a body-segment. Silurian
(Melb.) Victoria

]

=Jurassic Insects.--=

Of the group of the _INSECTA_, the Ipswich Coal measures (Jurassic) of Queensland have yielded an interesting buprestid beetle (_Mesostigmodera_), whilst beds of the same age in New South Wales contain the remains of a probable _Cicada_, associated with leaves of the fern _Taeniopteris_.

=Lower Cretaceous Dragon-fly.--=

From the Lower Cretaceous of the Flinders River district, Queensland, there has been obtained a fossil dragon-fly, _Aeschna flindersensis_ (Fig. 120 D).

=Cainozoic Insects.--=

Certain Cainozoic beds of New South Wales, of the age of the Deep-leads of Victoria, and probably equivalent to the Kalimnan terrestrial series, contain a species of _Cydnus_, a bug-like insect belonging to the order Rhynchota; and there are in the same series a Midge (_Chironomus_), a Day-fly (_Ephemera_, Fig. 120 E) and several beetles (? _Lagria_, _Palaeolycus_, _Cyphon_ and _Oxytelus_). The occurrence of these insects of the Deep-leads helps to complete the landscape picture of those far-off Lower Pliocene times, when the old river systems brought down large contributions of vegetable waste from higher lands, in the form of twigs with leaves and fruits; with occasional evidences of the rich and varied fauna of insect life which was especially promoted in the damp and vegetative areas of the lower lands.

COMMON OR CHARACTERISTIC SPECIES OF THE FOREGOING CHAPTER.

TRILOBITES.

_Ptychoparia howchini_, Eth. fil. Lower Cambrian: South Australia.

_Dolichometopus tatei_, H. Woodward. Lower Cambrian: South Australia.

_Olenellus browni_, Eth. fil. Lower Cambrian: Northern Territory.

_Agnostus australiensis_, Chapm. Upper Cambrian: Victoria.

_Ptychoparia thielei_, Chapm. Upper Cambrian: Victoria.

_Dikellocephalus florentinensis_, Eth. fil. Upper Cambrian: Tasmania.

_Dinesus ida_, Eth. fil. Lower Ordovician: Victoria.

_Asaphus illarensis_, Eth. fil. Ordovician: Central S. Australia.

_Ampyx parvulus_, Forbes, var. _jikaensis_, Chapm. Silurian
(Melbournian): Victoria.

_Illaenus jutsoni_, Chapm. Silurian (Melbournian): Victoria.

_Proetus euryceps_, McCoy. Silurian: Victoria.

_Cyphaspis spryi_, Gregory. Silurian (Melbournian): Victoria.

_Bronteus enormis_, Eth. fil. Silurian (Yeringian): Victoria.

_Lichas australis_, McCoy. Silurian (Yeringian): Victoria.

_Odontopleura jenkinsi_, Eth. fil. Silurian: New South Wales. Silurian
(Yeringian): Victoria.

_Encrinurus punctatus_, Brunnich sp. Silurian: New South Wales.
Silurian (Yeringian): Victoria.

_Encrinurus (Cromus) murchisoni_, de Koninck. Silurian: New South
Wales.

_Encrinurus (Cromus) spryi_, Chapm. Silurian (Melbournian): Victoria.

_Calymene blumenbachii_, Brongn. Silurian (Wangapeka Series): New
Zealand.

_Homalonotus expansus_, Hector. Silurian (Wangapeka Series): New
Zealand.

_Homalonotus knightii_, König. Silurian (Wangapeka Series): New
Zealand.

_Homalonotus harrisoni_, McCoy. Silurian (Melbournian): Victoria.

_Homalonotus vomer_, Chapm. Silurian: Victoria.

_Cheirurus insignis_, Beyrich. Silurian: New South Wales.

_Phacops sweeti_, Eth. fil. and Mitch. Silurian: New South Wales.
Silurian (Yeringian): Victoria.

_Phacops serratus_, Foerste. Silurian (Yeringian): Victoria. Silurian:
New South Wales.

_Dalmanites meridianus_, Eth. fil. and Mitch, sp. Silurian: New South
Wales, Victoria and Tasmania.

_Cheirurus_ sp. Middle Devonian: Victoria.

_Proetus_ sp. Devonian: Western Australia.

_Phillipsia seminifera_, Phillips. Carbopermian: New South Wales.

_Phillipsia grandis_, Eth. fil. Carbopermian: W. Australia and
Queensland.

_Griffithides eichwaldi_, Waldheim. Carbopermian: New South Wales and
Queensland.

_Brachymetopus strzelecki_, McCoy. Carbopermian: New South Wales.

PHYLLOPODA.

_Leaia mitchelli_, Eth. fil. Upper Carboniferous: New South Wales.

_Estheria coghlani_, Cox. Trias: New South Wales.

_Estheria minuta_, Alberti sp. Trias: New Zealand.

_Estheria mangaliensis_, Jones. Jurassic: Queensland.

OSTRACODA.

_Leperditia_ sp. Lower Cambrian: S. Australia.

_Beyrichia kloedeni_, McCoy. Silurian (Yeringian): Victoria.

_Beyrichia wooriyallockensis_, Chapm. Silurian (Yeringian): Victoria.

_Beyrichia maccoyiana_, Jones, var. _australis_, Chapm. Silurian:
(Yeringian): Victoria.

_Bythocypris hollii_, Jones. Silurian (Yeringian): Victoria.

_Macrocypris flexuosa_, Chapm. Silurian (Yeringian) Victoria.

_Primitia reticristata_, Jones. Silurian (Yeringian): Victoria.

_Leperditia shearsbii_, Chapm. Silurian: New South Wales.

_Primitia cuneus_, Chapm. Middle Devonian: Victoria.

_Beyrichia varicosa_, T. R. Jones. Carboniferous: Queensland.

_Primitia dunii_, Chapm. Carbopermian: New South Wales.

_Jonesina etheridgei_, Chapm. Carbopermian: New South Wales.

_Entomis jonesi_, de Koninck. Carbopermian: New South Wales.

_Synaphe mesozoica_, Chapm. sp. Trias: New South Wales.

_Cythere lobulata_, Chapm. Jurassic: W. Australia.

_Paradoxorhyncha foveolata_, Chapm. Jurassic: W. Australia.

_Loxoconcha jurassica_, Chapm. Jurassic: W. Australia.

_Cytheropteron australiense_, Chapm. Jurassic: W. Australia.

_Bairdia amygdaloides_, Brady. Cainozoic and living: Victoria.

_Cythere senticosa_, Baird. Cainozoic. Also living: Victoria.

_Cythere clavigera_, G. S. Brady. Cainozoic and living: Victoria.

_Cytherella punctata_, G. S. Brady. Cainozoic and living: Victoria.

_Cytherella pulchra_, G. S. Brady. Cainozoic and living: Victoria.

CIRRIPEDIA.

_Turrilepas mitchelli_, Eth. fil. Silurian: New South Wales.

_Turrilepas yeringiae_, Chapm. Silurian (Yeringian): Victoria.

_Lepas pritchardi_, Hall. Cainozoic (Janjukian): Victoria.

_(?) Pollicipes aucklandicus_, Hector sp. Cainozoic (Oamaru Series):
New Zealand.

_Balanus_ sp. Cainozoic (Janjukian and Kalimnan): Victoria.

PHYLLOCARIDA.

_Rhinopterocaris maccoyi_, Eth. fil. sp. Lower Ordovician: Victoria.

_Hymenocaris hepburnensis_, Chapm. L. Ordovician: Victoria.

_Caryocaris marri_, Jones and Woodw. L. Ordovician: Victoria and
Tasmania.

_Caryocaris angusta_, Chapm. L. Ordovician: Victoria.

_Saccocaris tetragona_, Chapm. L. Ordovician: Victoria.

_Ceratiocaris_ cf. _murchisoni_, Agassiz sp. Silurian: Victoria.

_Ceratiocaris pinguis_, Chapm. Silurian (Melbournian): Victoria.

_Ceratiocaris pritchardi_, Chapm. Silurian: Victoria.

_Aptychopsis victoriae_, Chapm. Silurian (Melbournian): Victoria.

_Dithyrocaris praecox_, Chapm. Silurian (Melbournian): Victoria.

DECAPODA.

_Prosopon etheridgei_, H. Woodw. Lower Cretaceous: Queensland.

_Ommatocarcinus corioensis_, Cresswell sp. Cainozoic (Janjukian):
Victoria.

_Ebalia_ sp. Cainozoic (Kalimnan): Victoria.

_Harpactocarcinus tumidus_, H. Woodw. Cainozoic (Oamaru Series): New
Zealand.

_Thalassina emerii_, Bell. (?) Pleistocene: Queensland and Northern
Territory.

EURYPTERIDA.

_Pterygotus australis_, McCoy. Silurian (Melbournian): Victoria.

INSECTA.

_Mesostigmodera typica_, Etheridge fil. and Olliff. Jurassic:
Queensland.

_(?) Cicada lowei_, Etheridge fil. and Olliff. Jurassic: New South
Wales.

_Aeschna flindersensis_, H. Woodward. Lower Cretaceous: Queensland.

_Chironomus venerabilis_, Eth. fil. and Oll. Cainozoic: New South
Wales.

_Ephemera culleni_, Eth. fil. and Oll. Cainozoic: New South Wales.

_Palaeolycus problematicum_, Eth. fil. and Oll. Cainozoic: New South
Wales.

* * * * *

LITERATURE.

TRILOBITES.

McCoy, F. Prod. Pal. Vict., Dec. III. 1876, pp. 13-20, pls. XXII.
and XXIII. (Silurian). Hector, J. Trans. N.Z. Inst., vol. IX.
1877, p. 602, pl. XXVII. (_Homalonotus_). Woodward, H. Geol.
Mag., Dec. III. vol. I. 1884, pp. 342-344, pl. XI. (Cambrian).
Mitchell, J. Proc. Linn. Soc. New South Wales, vol. II. 1888,
pp. 435-440, pl. XI. (Silurian). Foerste, A. F. Bull. Sci. Lab.
Denison Univ., vol. III. pt. V. 1888, pp. 122-128, pl. XIII.
Etheridge, R. jnr. Proc. Linn. Soc. New South Wales, vol. V.
pp. 501-504, pl. XVIII. (_Bronteus_). Idem, Parl. Papers, Leg.
Assemb. S.A., vol. I. No. 23, 1892; ibid., vol. 2, No. 52, 1893
(_Asaphus_). Id., Geol. Queensland, 1892, pp. 214-216, pls.
VII. VIII. and XLIV. (Carboniferous). Id., Proc. R. Soc. Vict.,
vol. VI. (N.S.), 1894, pp. 189-194, pl. XI. (_Bronteus_). Id.,
ibid, vol. VIII. (N.S.), 1896, pp. 56, 57, pl. I. (_Dinesus_).
Id., Rec. Austr. Mus., vol. V. No. 2, 1904, pp. 98-101, pl. X.
(Cambrian). Id., Trans. R. Soc. S. Austr., vol. XXII. 1898, pp.
1-3, pl. IV. (Cambrian). Etheridge, R. jnr. and Mitchell, J.
Proc. Linn. Soc. New South Wales, vol. VI. 1892, pp. 311-320, pl.
XXV.; ibid., vol. VIII. 1894, pp. 169-178, pls. VI. VII.; ibid.,
vol. X. 1896, pp. 486-511, pls. XXXVIII.-XL.; ibid., vol. XXI.
1897, pp. 694-721, pls. L.-LV. Tate, R. Rep. Horn Exped., 1896,