Cythere.[463]—This animal differs but little from Cypris except in having an additional pair of feet. In the Subgenus Cythereis the valves are thick, oblong, and strongly hinged; thus differing from the thin and more or less oval valves of the true Cythere and of Cypris. Several species of Cythere and its sub-genera occur in the Tertiary, Cretaceous, Oolitic, Liassic, Permian, and Carboniferous deposits.[464]
[463] For description and illustration of this genus, see Baird’s British Entomostraca, p. 163, &c.
[464] Consult M. Bosquet’s Memoir on the Tertiary Entomostraca of Belgium and France; Mr. T. R. Jones’s Monograph of the Cretaceous Entomostraca (Palæontographical Society), and of the Permian Entomostraca, in Prof. King’s Monograph of the Permian Fossils (Palæont. Soc.); and Prof. M’Coy’s Synopsis of the Characters of the Mountain Limestone Fossils of Ireland.
Three species of Entomostraca, very closely related to Cypridina,[465] from the Carboniferous rocks of Belgium, hare been figured and described by M. De Koninck; one species from the Carboniferous rocks of Ireland, by Prof. M’Coy;[466] and two species from the Cretaceous limestone of Maestricht,[467] by M. Bosquet. The genera Cyprella and Cypridella have been established by M. De Koninck for the reception of some allied forms found in the Carboniferous strata of Belgium; and Entomoconchus (M‘Coy) and Daphnoidia (Hibbert) are allied British Carboniferous forms.
[465] See Baird’s British Entomostraca, p. 176, &c.
[466] Under the name of Daphnia primæva.
[467] Under the generic appellation of Cyprella.
Trilobites.—Among the numerous petrifactions which are found in the limestones in the neighbourhood of Dudley, in Staffordshire, there are certain fossil bodies which, from their extraordinary form and appearance, have for more than a hundred and fifty years been objects of great interest to the naturalist, and of wonder to the general observer, and have long been provincially termed Dudley insects, or locusts.[468] By the earlier naturalists these fossils were referred to fishes, to molluscs, and to insects, before their real character was discovered. The most common type consists of a convex, oblong body, divided transversely into three principal parts, and longitudinally into three lobes, by two deep, parallel furrows; this last character suggested the name Trilobita, or Trilobites, by which the family is now distinguished by naturalists.
[468] Lhywd. Philos. Trans. for the year 1698.