PROZEUGLODON. 



245 



Z. osiris occurs, and above that of Protocetus. Eocefus of Fraas also belongs to this 

 horizon, and the large skulls and other remains mentioned by.Beadnell as occurring 

 in the same locality may belong to that genus or to Z. isis. 



The material available for description consists of a skull with the. right ramus of the 

 mandible, the base of the skull, the posterior end, and right side, of the palate being 

 imperfect; also portions of another skull and the three anterior cervical vertebrae 

 in a beautiful state of preservation. 



Skull (PI. XXI. ; text-figs. 80-82).— The occipital surface is broad (PI. XXI. 

 fig. 1 c ; text-fig. 81), and its upper portion is comparatively flat, the latera;l portions 

 of the supraoccipital (soc.) vs^hich form the posterior face of the greaOambdoidal crest 

 not being reflected backwards at the sides as in Z. osiris ; the supraoccipital, in fact, 

 is apparently flatter even than in the earlier Protocetus atavus, according to Fraas. 



Text-fig. 81. 



fier. 



Post"erior surface of skull of Frozeuylodo-k^atrox. -~. ._ 



6oc., basioccipital ; e.ro., exoccipital ; /.m., foramen magnum ; pa., parietal ; -per., periotic ; 

 soc, supraoccipital ; sg'., squamosal. \ nat. size. 



The condyles (cond.) are relatively larger than in Z. osiris ; they are strongly convex 

 from above downwards, and appear to have run down so that their narrow ventral 

 portions are separated from one another in the middle line by a short interval only, 

 and must have been formed in part by the basioccipital. Above the foramen magnum 

 if-m.) the exoGcipitals {eoco.) meet in a median suture, excluding the supraoccipital 

 from the opening ; laterally they run out into a broad wing-like expansion, the upper 

 edge of which unites with the posterior border of the squamosal {sq.), but laterally 

 is separated from that bone by the intercalation of a strip of the mastoid portion of the 

 periotic {per.), very narrow above, but widening out below. This lateral expansion 



