On a New Species of A&ocidm from the Tertiary of Georgia. 

 By E. D. Cope. 



Professor George Little, State Geologist of Georgia, placed in my hands 

 for determination a Chelonite from a Tertiary formation in Macon Co. of 

 that State. The matrix is a rather soft limestone of a light drab color. 

 When the specimen was first obtained it was nearly perfect, lacking only 

 the posterior part of one side, and the posterior border of the carapace. 

 Having been mutilated by destructive curiosity hunters, there remain now 

 the plastron and the anterior half of the carapace, with a considerable por- 

 tion of the posterior part of the left margin. The surface has been exposed 

 to the weather so as to obscure, and in some places to obliterate the dermal 

 sutures, while the skeletal sutures are distinct. The form has been slightly 

 distorted by lateral pressure, but not much. 



The obscurity of the dermal sutures renders the determination of the ge- 

 neric affinities somewhat difficult. The skeleton preserves the Emydoid 

 type, not exhibiting intersternal bones, and having a well developed me- 

 sosternum. The vertebral bones extend to between the sixth pair of cos- 

 tals, beyond which the specimen is imperfect in that region. The costal 

 capitula are well developed, but whether they reach the vertebral centra, 

 the specimen does not permit me to discover. The plastron is of peculiar 

 form, the lobes being short and contracted. The anterior is rounded from 

 a base of usual width, while the posterior, from a similar base, narrows 

 rapidly to a point, as in the genus Aromochelys. 



An important point is observed in the direction of the abdomino-pectoral 

 dermal suture. At its lateral extremities instead of continuing to the mar- 

 ginal scuta as in Emydoid genera, it turns forward and terminates at the 

 inguinal notch, as in genera with intermarginal plates, as Adocus and Der- 

 matemys. But the sutures of the intermarginals in the specimen are, if 

 they ever existed, very obscure, owing to exposure to the weather. Never- 

 theless there is sufficient indication of them on one side, to render it toler- 

 ably safe to infer their existence. Anterior to the abdomino-pectoral 

 suture, the border of the plastron is crossed by emarginations representing 

 three scutal sutures, defining the humeral, gular, and intergular scuta. 

 The courses of these sutures across the plastron are obscure. The huinero- 

 pectoral suture commences on the margin just in front of the axilla and ex- 

 tends forwards parallel with the border, becoming a deep open groove, 

 which is apparent on both sides of the plastron. It then turns backwards, and 

 appears to cross the plastron behind the mesosternum, presenting a concav- 

 ity forwards. The next suture in front appears to cross near the middle of 

 the mesosternal bone, presenting a strong concavity forwards. The rela- 

 tion between the intergulars and the gulars is difficult to discover. The 

 suture between them at the free margin is distinct, but after proceeding in- 

 wards a short distance it appears to divide and take two directions. One 



