130 



BATRACHIA. 



observed. Dolichosoma has at least 150 vertebrae and sometimes 

 approaches a metre in length ; it is not known to exhibit a 

 dermal armature. Ophiderpeton has the ordinary ventral shield 

 of oat-shaped scutes, and seems to have been armoured with 

 small dermal tubercles on the back. 



Sub-Order 3. Microsauria. 



The most numerous Stegocephalia of Upper Carboniferous 

 and Lower Permian age present the outward form of lizards or 

 salamanders, and have been provisionally grouped together 

 under the name of MICROSAURIA. In these animals, so far 



FIG. 85. 



Diagrams of Pelvic Arch of Stegocephalia, enlarged. A. Branchiosaurus. 

 B. Pelosaurus. c. Discosaurus. D. Petrobates. i, ilium ; is., ischium ; 

 p, pubis. (After Credner.) 



as known, the basioccipital region of the cranium is always 

 ossified. The hollow, conical teeth exhibit simple or only 

 slightly folded walls. The vertebrae (fig. 83 3, 4, 5) are con- 

 stricted cylinders, while the ribs are slender and longer than is 

 usual in the Stegocephalian order. The pubis is always ossified 

 (fig. 85 c, D). The degree of ossification of the carpus and 

 tarsus varies, and these regions are often entirely cartilaginous. 

 Very rare and perhaps doubtful instances are recorded in which 

 immature individuals exhibit traces of branchial arches (e.g., 



