175 



described, recent or extinct. The carapace and plastron, while being com- 

 pletely ossified as in Testudines, Emydes, &c, are ornamented in a manner 

 only seen to the same degree in the soft-shelled turtles. True, we see some- 

 thing like ornamentation of the same kind in some of the Emydes, but in 

 them the condition is coniparatively feeble. The osseous shell also appears 

 to be devoid of the usual outlines more or less strongly expressed of the in- 

 vesting scutes. A few of the plates exhibit obscure lines, but I am uncertain 

 as to whether they accord with the areas of the scutes. 



The outline of the carapace is broadly cordiform and somewhat resembles 

 that of the ordinary sea-turtles, but is not acute posteriorly as in these, being 

 obtuse as in the Emydes. The prominence of the carapace is moderate as in 

 the less elevated forms of the latter. It is uniformly convex, except that it 

 is acutely carinated in the median line posteriorly. 



The margin of the carapace anteriorly is rather obtuse, but laterally and 

 posteriorly is quite sharp. It is broadly and concavely notched in front ; the 

 first pair of marginal plates being the most prominent portions anteriorly. 

 Ante ro-late rally it is slightly concave, and from this position posteriorly is 

 uniformly convex. 



The plastron with its bridges is flat, and is intermediate in its relative pro- 

 portions with that of the snappers and Emydes. The bridges articulate with 

 the carapace by gomphosis, as seen in Fig. 2. They join the marginal plates 

 from the fifth to the eighth inclusive The extremities of the plastron are 

 both broken away in the specimen. 



The vertebral plates of the carapace are narrow coffin-shaped. Those an- 

 terior are nearly level ; those posterior are acutely carinated. 



The costal plates within exhibit no costal elevation, but are quite level, as 

 represented in Fig. 3. The costal capitula are unusually broad but thin. 



The inner surface of the nuchal plate at the posterior border presents a 

 pair of round articular processes for conjunction with the contiguous vertebra. 



The upper surface of the carapace is ornate with rugosities. These are 

 obsolete on the vertebral plates. On the costal plates they appear as longi- 

 tudinal, undulating, and nearly parallel ridges crossing the plates. Internally 

 they are feebly developed and become more strongly marked proceeding out- 

 wardly. 



On the marginal, including the nuchal and pygal plates, the rugosities are 

 finer, closer, more interrupted, and in part even granular. 



