Il8 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



coid. A pair of small elements lie one on either side ot the clavicles and Jaekel (347) 

 interprets them as the cleithra. If they are cleithra they are unique among the 

 Microsauria. The pectoral girdle does not, however, indicate that Diceratosaurus 

 is "unique among all known quadrupeds." 



Jaekel regards the limb which is preserved with the material as an arm (plate 

 1 5, fig. 4) , but there is no reason stated for his conclusion. It has all of the characters 

 of the leg and may be regarded as such. Only a part of the lower end of the femur is 

 preserved. The tibia and fibula are preserved as separate rod-like elements with one 

 of the bones longer and larger, probably the tibia. There are 5 toes which have the 

 customary phalangeal formula for a microsaurian foot of 2-3-3-4(?)-3. The 

 tarsals are unossified. 



The vertebrae (plate 15) were perforated for the notochord, and are hour-glass- 

 shaped, with the neural arch thickened to support a heavy spine which bore a sculp- 

 tured plate. These apical plates occur in the dorsal region, but diminish toward the 

 caudal vertebrae. The number of the vertebrae in the dorsal region is very small and 

 in the tail very large. There are possibly 2 vertebrae in the cervical, 1 1 in the dorsal 

 series; the thirteenth carries the pelvis. There are over 100 vertebrae in the tail. 



The ribs have an expanded head and the transverse processes of the vertebrae 

 are long. 



The following account is based on the writer's study of the type specimen and 

 he is able to add several points of interest to a knowledge of the anatomy of the 

 type of this interesting microsaurian. 



The type specimen consists of 11 consecutive vertebrae with a portion of the 

 skull, the greater portion of the pectoral girdle, parts of both fore limbs, ribs, and 

 ventral scutelte (plate 14, fig. 4). The species is represented in the collection by yet 

 another specimen, on which Cope based his Tuditanus mordax (plate 22, fig. 5), of 

 which he himself says: "Further examination of the specimen on which the latter 

 ( T. mordax) was founded leads to the belief that it is an imperfect cranium of Cerater- 

 peton {Diceratosaurus) punctolineatum Cope." The plates referred to are rather to be 

 regarded as elements of the pectoral girdle and I believe they represent the clavicle 

 and a portion of the interclavicle. 



The skull of the present species is fully described by Jaekel. The type specimen 

 does not offer any evidence in support of Jaekel's "perisquamosal," but rather 

 tends to the idea that he is incorrect in his assumption of the fusion of these elements 

 of the skull. The direction taken by the ridges and grooves on the elements pre- 

 served indicate a separation between the supratemporal and the squamosal. I do 

 not find that the grooves have the tendency to arise from a common center of ossi- 

 fication in the squamosal, as suggested in the figures of Jaekel. The horn which 

 projects backward from the squamosal is rather large and heavy for the size of the 

 skull, and after curving slightly inward ends in a blunt point and not sharply, as 

 Jaekel figures in his specimens. The vertebral column is indistinctly preserved and 

 I have nothing to add to Jaekel's account given above. 



In the structure of the pectoral girdle my results are greatly at variance with 

 those of Jaekel. I do not find the remarkable elements which Jaekel has figured 



