analogies of structure, which place them in near approximation to the inhabitants of the existing seas.[1]
The anterior segment of the Trilobites (Pl. 46, a, passim,) is composed of a large semi-circular, or crescent-shaped shield, succeeded by an abdomen, or body (c,) composed of numerous segments folding over each other, like those in a Lobster's tail, and generally divided by two longitudinal furrows into three ranges of lobes, from which they have derived the name of Trilobites. Behind this body, in many species, is placed a triangular or semi-lunar tail or post-abdomen (d,) less distinctly lobated than the body. One of these Genera, the Calymene, has the property of rolling itself up into a ball like a common Wood-Louse. (See Pl. 46, Figs. 1, 3, 4, 5.)
The nearest approach among living animals to the external form of Trilobites is that afforded by the genus Serolis in the class Crustacea. (See Pl. 45, Figs. 6, 7.)[2] The most striking difference between this animal, and the
- ↑ See M. Audouin's Recherches sur les Rapports naturels qui existent entre les Trilobites et les Animaux articulés.
- ↑ The Genus Serolis was first established by Dr. Leach, on the authority of specimens collected by Sir Joseph Banks, in the Straits of Magellan (or rather of Magalhaens, the proper name of the navigator, according to Captain King) during Sir Joseph's voyage with Captain Cook, and given by Sir Joseph to the Linnaean Society; and of another specimen of the same Genus from Senegal given by Mr. Dufresne to Dr. Leach. From these Dr. Leach described and named the species represented in our plate; his description of this Genus is published in the Dictionnaire des Sciences Naturelles, v. 12, p. 340. Captain King has lately collected many specimens of Serolis on the east coast of Patagonia, lat. 45. S. 80 miles from the shore, and brought up by dredging in 40 fathoms water; and also at Port Famine, in the Straits of Magalhaens, where it was thrown upon the beach by the tide; here Captain King saw the beach literally covered with them dead; he has observed them alive swimming close to the bottom among the sea-weed; their motions were slow and gradual, and not like those of a shrimp; he never saw them swimming near the surface; their legs seemed shaped for swimming and crawling on the bottom.
