1896.] lOJ [Cope. 



Plate X. 



Dissorhophus articulatus Cope, American Naturalist, 1895, p. 998; por- 

 tion of skeleton, five-sixths natural size. 

 Fig. 1. Carapace from above. 



Fig. 2. Vertebral column ribs and carapace from below ; stime speci- 

 men as Fig. 1. 

 Fig. 3. Anterior extremity of same specimen. 



Lettering. 

 Q., Quadrate bone, Md., Mandible; Pg., Pterygoid; MA., Meatus 

 auditorius externus ; C7., Clavicle ; ^s., Episternum ; a'?!?.. Scapula ; Co., 

 Coracoid ; GL. Glenoid cavity; H., Humerus; Cu., Cubitus; Ce., Cen- 

 trum; Ic, Intercentrum ; Pc, Pleurocentrum ; Ns., Neural spine; E., 

 Eib ; Ca., Carapace; Fe., Femur; T., Tibia; Fi., Fibula. 



Sixth Contribution to the Knowledge of the Marine Miocene Fauna o/ 

 North America. 



By E. D. Cope. 



{Read before the American Philosophical Society, May 15, 1S96.) 



The fifth contribution was published in the Proceedings of the Society 

 for 189o, p. 13.1, and the fourth in the same for 1870, p. 270. 



Syllomus crispatus Cope, gen. et sp. nov. 



Char. gen. — Order Testudinata ; family probably Cheloniida?. Costal 

 bones developed beyond rib extremities, and uniting with marginals by 

 suture. Surface sculptured with grooves and ridges. Humerus with 

 entepicondylar foramen enclosed, and flattened shaft. Radial process 

 remote from head. 



This is the only definable form of Testudinata yet discovered in the 

 Yorktown bed of the Chesapeake region. It is quite rare, as I have met 

 w^ith it at one time and place only. The carapace is more fully 

 developed than in Chelone and Argillochelys, and it dift'ers from these 

 and from Lytoloma in the sculpture of the surface. From all of these 

 genera and from Peritresius it ditl'ers in the union of the marginal bones 

 with the costoids by suture. 



A few fragments of a species of Lytoloma have been found in the same 

 formation. 



Char, specif. — This tortoise is known to me from two incomplete 

 costal bones and a humerus. One costal fi-agment is distal, and the 

 other is proximal. The humerus has the deltoid crest broken off at the 

 base. 



The carapacial bones are very thin and consist of a thicker superior 



PROC. AMER. PHILOS. SOC. XXXV. 1.51. R. PRINTED AUGUST 13, 1896. 



