24 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



7. Clavicles and interclavicles without sculpture. 



8. Cleithrum present. 



9. Humerus heavy, ends at right angles to each other. 



10. Femur with prominent ridge on ventral surface. 



11. The two halves of the neural spine united. 



12. Intercentrum thick and heavy, nearly closing notochordal space. 



Genus ERYOPS Cope. 



Cope, Eryops, Proc. Am. Phil. Soc, vol. xvii, 1878, p. 188; Proc. Am. Phil. Soc, 



vol. XVII, 1878, p. 520; Proc. Am. Phil. Soc, vol. xix, 1880, p. 51. 

 Broili, Eryops, Paleontographica, Bd. xlvi, 1899, s. 61. 

 Cope, Epicordylus, Proc. Am. Phil. Soc, vol. xvii, p. 515. 

 Rhachitomus, Proc. Am. Phil. Soc, vol. xvii, p. 526. 



Type: A good skull with lower jaws and numerous vertebrae and bones 

 of the girdles. No. 4189 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: Of the genus Eryops, the original descriptions of 

 the synonyms are given below. 



"The skull is not elongate, and the quadrate bones are produced far 

 backwards. The epiotic processes are present, but not remarkably elongate. 

 The temporal fossa is covered by the usual roof. The orbits are round, pos- 

 terior in position, and small. There is no postorbital depression or groove, 

 and the lateral epiotic sinus is not deep. The nostrils are large and widely 

 separated. There is no angular process of the mandible. The maxillary 

 teeth are of different sizes, although arranged in a single row. The posterior 

 are small and not closely placed; large teeth appear anterior to the middle. 

 The premaxillary bone supports a number of large teeth. Those of the man- 

 dible which are visible in the specimen in its present state, those opposite 

 the nares, are of medium size. The form of the crowns of the teeth is conic, 

 with weak fore-and-aft cutting edges. There are no distinct fissures of the 

 surface although these may be represented by some fine parallel lines. 



"Vertebra referred to this genus are small in proportion to the dimensions 

 of the skull. They are not discoidal but somewhat elongate; are biconcave, 

 and are not perforated for the notochord. The middle portion of the cen- 

 trum is contracted. One articular extremity has the borders of the concave 

 center convex. Zygapophyses large. Ribs present, short; neural spines 

 elongate, stout." 



In the second paper Cope adds: 



"A series of a few large teeth much exceeding the maxillaries in size within 

 the latter, perhaps on the palatine bone. No row of smaller teeth within 

 the maxillary series, or on the vomer, as in Mastodonsaurus and Capitosaurus. 

 The choanae are large, and extend well forwards." 



In the third paper he gave an extended description: 



"The largest element of the vertebra is the intercentrum. This, which 

 occupies the entire inferior surface of the vertebra, is a segment, represent- 

 ing the sixth part of a sphere, with a slight central vacuity. The element 

 representative of the centrum is wedged in between the superior external 

 angles of adjacent intercentra, as in Trimerorhachis. These, as well as the 

 intercentra, differ from those of that genus in their greater degree of ossifica- 

 tion, which is so far complete as to greatly contract the canalis chorda dor- 

 salis. The central elements of opposite sides do not unite on the middle line 

 below, although in contact. The neurapophysis is produced downwards 



