| OCR Text |
Show 406 DR. J. E. GRAY ON THE GENERA OF TURTLES. [Apr. 1, and skull beneath it with a triangular ridge on each side, divided in front by a central longitudinal groove ; of the lower jaw concave, with a sharp edge on the outer and inner margin. Claw of the first finger moderate. 1. LEPIDOCHELYS. Head not so broad as long ; sides flat, angularly contracted in front. Dorsal shield keeled, the nuchal plate very broad, the first vertebral broader than long, the second and third much longer than broad; front fin with one small claw on the outer side. The nasal shields broader than long, the frontal plate elongate, six-sided, the parietal plate subtriangular, broader behind, covered in front by the hinder part of the frontal plate, many-angular on the sic'es, and with an arched-out hinder margin. Occipital shield single, transverse, large, rounded in front, truncated behind, Superocular shields three on each side; the front one square, united with the opposite one in front of the frontal; the middle one largest, rather longer than broad ; and the third smallest, broader than long. The cheeks with a series of four shields, the upper being small and square. Upper beak with a slight central hook ; the alveolar surface with a ridge on each side, interrupted in the middle, rather closer to the inner edge than the outer one. Inner edge with a blunt raised margin. The alveolar surface of the lower jaw deeply concave, with a high acute ridge on the front and hinder margins, and a well-marked central longitudinal ridge across the concavity in front, which is more acute and higher behind, and with a broad deeply concave space behind the inner ridge. The upper alveolar surface of the beak of this species is very like that of Cephalochelys; but the lateral ridge on each side is nearer the hinder margin, and the surface behind it is not only margined on the edge, but is much narrower. In some respects the upper alveolar surface is more allied to that of Chelonia; but the lateral ridges are much further from the outer margin, and the alveolar surface of the lower beak is narrower, with a more decided central longitudinal ridge, and a much wider concave surface within the ridge ; and the beak itself is not nearly so high and strong. The sternum is callous on the three pairs of lateral bones, leaving a longitudinal soft space in the middle. The front pair of bones, which are short and V-shaped, and the broad lanceolate odd bone, which is broad and angular in front and produced and tapering behind, about once and a half as long as broad, are only covered with a soft skin, which is transparent. The hinder vertebral bone in this adult specimen is broad, the whole width of the two posterior marginal plates. There can be no doubt that it is quite a different genus from the common Loggerhead (Caouana), not only in the form of the last vertebral bone, but also in the shape of the shields of the head. The number of the costal shields is increased by what are usually considered the fourth and fifth being divided in half, so that there is a distinct shield over each of the hinder ribs, instead of one to |
