6 FOSSIL CHELONIAN REPTILES OF THE 



and covered the posterior half of the hyosternals and the anterior third of the meso- 

 stemals. The abdominal scutes, a h, presented a similar form, and covered the rest of 

 the mesosternals and less than half of the hyposternals. The femoral scutes, fe, were 

 longer than they were broad ; they jomed the abdominal scutes by a straight transverse 

 line ; but that between them and the anal scutes, a n, describes a curve, with the con- 

 vexity backwards, and nearly equally divides the xiphisternals, xs. In addition to the 

 axillary and inguinal scutes, there are three scutes interposed between the outer borders 

 of the pectoral and abdominal scutes, and the under borders of the fifth, sixth, and 

 seventh marginal scutes : these superadded scutes I propose to call " submarginal 

 scutes." The Plati/sternon megaceplialum, or Large-headed Terrapene of the Chinese 

 swamps, presents a corresponding, but single, supplementary " submarginal scute," 

 upon the under part of each lateral production of the plastron. The under surface of 

 the fifth, sixth, and seventh marginal plates bears a crucial impression, indicative of 

 the lines of junction between the marginal and submarginal scutes. The head of the 

 left femur is preserved, near the seventh marginal plate, in the specimen above 

 described. 



For the species of Pleurosternon, which the above-described specimen. Tab** II and 

 III, represents, I propose the name of concinnum. 



Pleurosternon EMARGiNATUM. Owen. Tab* IV, V, and VI. 



A nearly-allied species, Pleurosternon emarginatum, is represented in Tab*^ IV, V, 

 and VI. It is from the same formation and locality, and differs from the foregoing 

 chiefly in the contour of the free borders of the plastron. The anterior and posterior 

 marginal plates being preserved in the specimen figured in Tab. IV, and almost all 

 those of the right side in that figured in Tab. V, we obtain a nearly complete idea of 

 the contour of the carapace in this broad and depressed extinct species of Emydian. 

 The nuchal and first marginal scutes are unluckily wanting in the specimen with the 

 upper surface of the carapace exposed, which prevents our determining whether the 

 present species possessed or not the nuchal scute. The neural plate answering to & i 

 in ordinary Chelonia is divided by a transverse suture in this species, as in PI. concinnum. 

 Tab. II ; and the impression of the line of union between the first and second vertebral 

 scutes crosses just in front of the suture of division. The second neural plate, 2, joins 

 the first costal plate of the left side, but not that of the right ; and it is pentagonal, 

 the shortest side or border being that which joins the left first costal plate. The 

 third, 3, to the seventh, 7, neural plates inclusive are hexagonal, and resemble in 

 shape those in the Pleurosternon concinnum; the eighth neural plate is hexagonal, and 

 is broader than it is long ; the ninth neural plate, answering to that bearing the letter « 8 

 in Tab. II, is more expanded at its hinder part ; the tenth neural plate, 10, is triangular, 



