Figure 12. — Teeth of the saw shark, Pristiopho-rus 

 schroederi (Pristiophoroidea), showing a modified al- 

 ternate tooth arrangement differing from the arrange- 

 ment found in the Scyliorhinidae (Galeoidea) chiefly 

 in the lesser degree of crowding. Photograph by Los 

 Angeles County Museum. 



Scyliorhinidae, and the false cat sharks, Pseudo- 

 triakidae, already have been noted. The upper 

 and lower jaw teeth of Pseudotriakis microdon 

 Bocage and Capello are illustrated in Bigelow and 

 Schroeder (1948) and are described and discussed 

 in more detail by Jaquet (1905). The arrange- 

 ment of teeth in the lower jaw in Pseudotriakis 

 and Apristurus have some similarity in ap- 

 pearance due to the rather well defined diagonal 

 files of teeth. Gross examination of the type spec- 

 imen of Pseudotriakis acrages Jordan and 

 Snyder (SU 12903) shows the diagonal files of 

 lower jaw teeth continuing widely separated, but 

 with the teeth within a file quite close together, 

 back to the germinal area (see fig. 13). This ap- 

 pears to indicate a diagonal movement of the teeth 

 from the area of budding into the functional posi- 

 tion, but such an explanation is superficial. A 

 study of the comparative histology of the develop- 

 ing teeth in several families of sharks should prove 

 helpful in indicating relationships. 



NUMBER OF VERTEBRAE 



Vertebrae were counted from radiographs of 

 specimens of the family, but the diplospondylous 

 vertebrae near the tail tips were difficult to count. 



Figure 13. — Upper photograph showing diagonal files 

 of teeth in the lower jaw of the type specimen of 

 Pseudotriakis acrages Jordan and Snyder (SU 

 12903). Lower photograph, same jaw rolled out- 

 ward with the tooth germinal area exposed and 

 showing .continuation of the files diagonally on the 

 dental lamina where they become progressively 

 smaller and softer to the point of their apparent 

 origin. 



Furthermore, in some radiographs it was not pos- 

 sible to determine whether all of the terminal ver- 

 tebrae appeared. Since it was always possible to 



REVIEW OF WESTERN ATLANTIC CAT SHARKS 



595 



