144 



THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



This species is one of the most abundant of the Linton Amphibia. Cope based 

 his description of the species on 9 specimens. There are more than two dozen avail- 

 able at the present time, the majority of them being in the possession of the Amer- 

 ican Museum of Natural History. There is a single specimen in Walker Museum 

 of the University of Chicago and 3 in the United States National Museum. The 

 numbers of all of these specimens are given above. The material consists, for the 

 most part, of fragmentary portions of the vertebral column, but there are a few 

 skulls more or less complete, though none are sufficiently well preserved for a com- 

 plete analysis of the characters. The specimens indicate an animal slightly smaller 

 than the modern Aiii/>liiiuiia means of the Mississippi River. 



It will not be necessary here to enter into a detailed account of each specimen, 

 since this has been done by Cope, and a careful comparison of his descriptions with 

 the originals indicates that his observations are correct. The species, as suggested 

 in the discussion of the genus, is not clearly distinct from those of Ptyonins, and it 

 has largely the characters of that genus. The cranium is long, slender, and wedge- 



Fa.. 31. Restoration of CEstoccphalus. X I. 



shaped. The teeth arc numerous both in the maxillary and in the mandible, one 

 specimen indicating about 30 in a single series. They are all uniformly cylindrical, 

 except at the extremity, where they are flattened and expanded so as to produce a 

 longitudinal edge, which is carried backward on a recurvature of the apex. The 

 bases are anchylosed equally and without enlargement, and no part of the shaft is 

 striate or grooved. The upper surface of the cranium is narrow, with the median 

 suture distinct. The skull surface, with that of the mandible, is smooth. 



Characteristic of the species are the remarkable length and slenderness of the 

 fan-shaped neural and haemal spines, and the absence of an acute serration on their 

 margins. In this species the spines have a laminiform expansion at the base in 

 their plane. One specimen exhibits the pelvic region, including a portion of the 

 tail. The ilium has an expanded anterior extremity and is directed backwards 

 and somewhat inwards on either side of the vertebral column. The femur is nearly 

 straight, short, contracted medially, and expanded distally. The tibia is shorter 

 and is subcylindrical. Beneath the ilium the last chevron of the abdominal rods 

 appears, the outer extremities rising on the base of the tail. 



The pectoral arch is almost unknown, and Cope based the distinction of Ptyo- 

 nins, and (Estocephalus on the absence of these plates in the latter genus an uncer- 



