236 S. W. WILLISTON. 



unpaired supraoccipital, the absence of pineal foramen, quadra- 

 tojugals, jugals, postfrontals, temporal arches, the evidently large 

 parasphenoid, the double occipital condyles, paired branchials, 

 neurocentral, single-headed ribs, etc., are positive evidence that 

 the animal is not only not a reptile but that it is related to the 

 modern urodele amphibians. In skull structure the characters are 

 urodelan in every detail save the separated " epiotics," the inter- 

 calary of Cuvier, Vrolik and Cope, the paroccipital plates of 

 Baur, the posttemporals of Broom ; and this separation is pre- 

 cisely what would be expected in the early urodele. The ex- 

 occipitals otherwise seem to be a single bone in Lysorophns, but 

 it is very probable that they are the result of an early fusion of 

 the exoccipitals, paroccipitals and prootics. The squamosals and 

 quadrates have the position and relations of modern salamanders, 

 the quadrate rather better ossified than is usually the case. That 

 the supraoccipital should be ossified is, also, what might be ex- 

 pected. The remarkable fact that this bone should be unpaired 

 while all the remainder of the bones of the skull are very loosely 

 joined, as also the fact that the corresponding element in the 

 urodeles is cartilaginous would seem to preclude its identification 

 with the paired supraoccipital plates, the postparietals of Broom, 

 of the Stegocephalia, rather favoring Gaup's contention of the 

 nature of his tectum sjnoticuni. 



The tricarinate structure of the vertebral centra is quite aber- 

 rant for a reptile, but not remarkable for a urodele ; so also is 

 the sutural division of the neurocentra, and, for the Permian, the 

 neurocentral attachment of the single-headed ribs. The only 

 aberrant character to distinguish LysoropJuis from the Urodela is 

 the long and rather broad ribs, unknown among these modern 

 animals or their possible ancestors the Branchiosauria. It is, 

 however, very evident that the earliest ancestors of both these 

 groups must have long ribs, and their persistence in Lysorophiis 

 would be nothing remarkable. Nor do I think it impossible that 

 Lysoroplms and its immediate kin may have developed long ribs 

 from the earlier short ones. Certain it is that this character 

 alone, and it is the only aberrant one, should not exclude 

 Lysoroplms from the Urodela, though it may necessitate a slight 

 revision in the definition of the group. That Lysoroplms cannot 



