6 4 



THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



The animal, from the shape and form of the ribs, is undoubtedly a branchio- 

 saurian, since short, heavy, straight ribs have not yet been found to be associated 

 with other than branchiosaurian structures. It is placed in the genus Mazonerpeton 

 on account of the structure of the pectoral elements, the form of the humerus, and 

 the length of the tail, all of which agree in structure with Mazonerpeton loiigicandn- 

 tuiii. The animal attained, perhaps, a length of 4.5 inches, while that of M. longicau- 

 datum was about 3 inches. The tail in the present species is very long and slender, 

 more elongate than in any other known branchiosaurian. 



The part of the skull preserved is very unsatisfactory and, aside from the fact 

 that it seems to represent the under side of the left half of the skull, little can be 

 said. Three sutures can be observed, but what sutures they are is undetermined. 

 The left mandible lies crushed on the edge of the skull and partially obscures what 

 little there is of that structure. The 

 slightly curved impression, from 

 which the bone has been either 

 broken or weathered, measures 13 

 mm. in length by 3 mm. in posterior 

 diameter by I mm. in anterior diam- 

 eter. These measurements show the 

 element to have been slender and 

 pointed anteriorly. 



Very little accurate information 

 can be derived from the study of 

 the vertebral column of the speci- 

 men, nor can the dorsal vertebral 

 formula be made out, since only a 

 portion of the length of that region 

 is preserved and only a few rather 

 indefinite impressions can be dis- 

 cerned. These impressions show 

 the vertebras to be short and higher 

 than in most Branchiosauria. 



The caudal series is represented by two sections, one of which is, apparently, 

 from near the base of the tail, judging from the size of the caudal ribs preserved; 

 the other is from near the tip of the tail, and shows the constituents to have been 

 long and slender. Ribs are apparently absent on this section. The position of the 

 two caudal sections shows that when the animal died it was coiled up much like a 

 snake, so that in the fractured nodule three sections of the body are visible. The 

 tail was probably half as long again as the body. 



The ribs throughout the body are short, heavy, and straight, with, in the dorsal 

 series, a lateral and a distal expansion which is taken as a distinctive specific char- 

 acter. Judging from imperfect impressions in the dorsal series, the ribs were 

 attached to a transverse process of the centrum, thus agreeing with other branchio- 



FIG. 146. Skeleton of Mazonerpeton costatum Moodie. X 1.5. 

 Original in Yale University Museum, dv, dorsal vertebra; 

 </i, neutral spines; cl, clavicle; cv, caudal vertebrae; /, femur: 

 /;, humerus; m, mandible; rb, rib; sk, skull; v, vertebrae. 



