366 ON THE SHOULDER-GIRDLE AND EXTREMITIES OF ERTOPS. 



This carpus and fore foot is noteworthy from the presence of five digits, an un- 

 usual character in the class Batrachia. The genus Archegosaurus has but- four, 

 although according to Baur* there are five carpalia. In the presence of two centralia, 

 Eryops agrees with occasional specimens of both Cryj)tohranc7tus allegheniensis and 

 Megalobatrachus japonicus (Wiedersheim). If three centralia are present, the resem- 

 blance to Archegosaurus decheni is greater, where, according to Baur, there are four. 



The posterior foot found at the same time and place as, and having appropriate 

 proportions to, the parts already described, is not so well preserved. The distal ele- 

 ments of the leg have subequal widths, but they are folded back to back so that one 

 of them has lost its tarsal connections. One of them, perhaps the tibia, remains 

 articulated to two proximal tarsals, probably tibiale and intermedium. The approxi- 

 mated surfaces of these bones are very thick, as is the internal fiice of the tibiale. 

 The external face of the intermedium is, on the conti-ary, thinned out. The tibiale is 

 characterized by the presence of a round, flat, discoid tuberosity on its ? posterior 

 face, which resembles the disc of a button. Distad from the tibiale is a large trans- 

 verse centrale, in the position of the Pelycosaurian and Mammalian navicular. It 

 articulates with the distal extremities of the intermedium as well. Its distal face 

 articulates with two tarsalia, which are somewhat displaced in the specimen. The 

 remainder of the foot is in two separate pieces, which represent probably parts of 

 both posterior feet. In one of these I count five metatarsal bones very much dis- 

 placed. Two of them are of rather small size. In the other block is a series of four 

 consecutive phalanges, all wider than long. The distal one is quite small, but the 

 ungual is not x^resent. 



Two small tarsi from opposite sides of perhaps the same individual were found 

 mixed vsrith the bones of the larger animal. They belong to an allied form. The 

 tibiale has the same button-like disc on one of its faces, and it articulates distally 

 with a navicular-centrale. The ? intermedium is a shorter bone and unites with a 

 single element, which may represent a centrale 2, or a cuboid. It appears to articu- 

 late distally with two elements, though the matrix does not let it be determined 

 whether the lines observed are sutures or fractures. And it is not certain whether 

 the two supposed elements are tarsalia or proximal ends of metatarsalia. There is, 

 as in the larger tarsus, no indication of an exterior or fibular series of tarsals. The 

 bone referred to as possibly cuboid, rises on the external side of the level of the 

 proximal face of the intermedium, and may be therefore a fibulare, which presents 

 very little proximal facet. This tarsus strongly suggests the presence of but four 

 digits. 



* Beitriige z. Morphogenie d. Carpus u. Tarsus d. Vertebraten, 1887, i, p. 53. 



