GEOLOGICAL SURVEY OF THE TERRITORIES. 625 



EMYS, Brong. 



Section Palfvotheca., Cope. 



Proceed. Auier. Pliilos. Society, 1872, p. 463 ; NotomorpM, \. c, 1872, p. 474. 



This genus is conii)Osed of Emydidm in which the inargiual and costal 

 bones are united by suture with the weak gomphosis of many of the 

 recent forms of the family. The plastron is united by sutural attach- 

 ment of the prolonged borders of the bridge to one or two adjacent 

 costal bones, in an elongate pit of greater or less elevation. This eleva- 

 tion may be so produced as to constitute axillary and inguinal septa as 

 in the recent genus Batcujur. In many of the species the anterior or 

 axillary suture is on a single costal, the posterior on the produced mar- 

 gins of two. Several of the species are of small size and with strongly 

 convex carapace. Some of these might be suspected to be young of 

 others already known, but for the fact that their component pieces are 

 generally more massive and their sculpture more pronounced. They 

 resemble in several silperflcial respects our Cistudines. 



I formerly (Extinct Batrachiaund Reptilia K. A., &c.) described a genus 

 Agomphus of the Cretaceous period as having the character of articula- 

 tion of the margiual bones without gomphosis ; in this some Eocene 

 forms agree with it. Additional specimens of A. petrosus, Cope, the type, 

 show that it possesses a series of intermargiual scuta as in Adocus and 

 Bermatemys. 



Some of the species {E. testudinea, &c.) I originally placed in a sepa- 

 rate genus, Nofomo)p]ia, on the supposition that they were pleurodire. 

 The costal articulations of the bridge are identical in form with those 

 of the pubis in many pleurodire genera, {Taphrosphys, e. g.,) and are so ob- 

 lique as to be similar to these in position also in relation to the lateral 

 sutures when the iiat costal is not complete. The species appear to be- 

 long to the present genus. 



Most of the smaller species were found in strata of the Green River 

 epoch, near Black Butte and Bvanston; the larger species occur in the 

 Bridger beds proper. The following is a synopsis of the species : 



I. The bridge sutures not or moderately elevated on a single costal at 

 one extremity of the carapace only. 



a. Dorsal line with a projecting keel. 



B. poiycyphus ;E. terrestris; E. megaulax; E. paeliylomus. 

 aa. Dorsal line not keeled. 



/3. Mesosternal not reached by gular scuta. 



E. tesfudincus; E. eiithnetus. 

 13,8. Mesosternal entire, bearing part of gular scuta. 



E. gravis ; E. wyomingensis ; E. latilahiatus. 



II. The bridge sutures on prominent septa, which are composed of ad- 

 jacent parts of adjacent costal bones. 



E. scjytarius. 



Emys septaeius. Cope. 



Established on a nearly complete specimen of the size of Pfychemys 

 rngosa. The carapace is rather thin and the sutures not obliterated. 

 The vertebme are sessile on the vertebral bones. The form is quite 

 convex. The plastron is iiat and rather stout. The mesosternum is 

 rhombic, the longer angle anterior on tlie outer side, but posterior on 

 the inner* side. Its anterior angle is embraced by the gular scuta. 

 Tlie anterior lobe of the plastron is contracted near the axilliB, and flared 

 with a thin edge in irunt of it; then contracted to the rather narrow li^) 



40 G S 



