EOCENE CHELONIA. 79 



Sternothcerus and Hydro-medusa, the nuchal scute is absent in Emys Conybearii, the 

 number of marginal scutes being 12 — 12. 



In Emys nigricans the nuchal scute is absent, and the number of marginal scutes 

 is as in Emys Conybearii. 



The carapace of Emys Conybearii is moderately convex at the middle, and very 

 slightly concave towards the margin, which is gently raised before and behind. 



The plastron, as in the section of Emydida, including Emys proper,* is solid, 

 truncate before and notched behind (T. XXVIII B), attached to the carapace by sutures 

 of bone. The number and character of the sternal plates I have been unable to deter- 

 mine : there is no transverse joint as in the Box-tortoises {Cistudo, Lutremys). 



The chief peculiarity of the plastron of the Emys Conybearii is the concavity of its 

 middle three fifths (T. XXVIII B, fig. 2) — a modification which is rarely seen save in 

 some true Tortoises. This character, coupled with the divided first vertebral scute, would 

 probably be deemed worthy of supporting a sub-generic distinction by some erpeto- 

 logists. 



* Gray, torn, cit., A, a, p. 15. It is called " sternum " in this work; but the " plastron " includes 

 many other elements of the skeleton besides the sternum ; to say nothing of the bony scutes, superadded 

 to the sternum and abdominal ribs. 



