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.”