EDENTATA OF THE SANTA CRUZ BEDS. 8 1 



Dentition. I have seen no specimen in which the number of upper 

 teeth could be definitely determined, but the dental formula would appear 

 to be TQ and, so far as I can judge, no tooth is implanted in the premaxil- 

 lary. In the upper jaw the two dental series converge anteriorly ; - 1 is very 

 small, compressed, and almost laminar ; it is separated from * by a con- 

 siderable diastema, which is a marked distinction from Prozaedius ; a is 

 somewhat larger and is separated from ^ by a diastema which is about 

 one-half as long as that between - and -; the remaining teeth follow with 

 the usual regular interspaces, increasing in size, especially in thickness, to 

 -, while & and - are slightly smaller ; most of them are of oval section 

 and bevelled by wear, with a central area of harder dentine. 



In the mandible the first four teeth are more widely spaced than the 

 last six, but there is no such diastema as in the upper jaw. These ante- 

 rior teeth are very much compressed and thin, while the succeeding teeth 

 increase in size to ^ which is the largest of the series. 



Skull (Plate VI, fig. 20). The skull is remarkable for its extreme elon- 

 gation, especially of the rostrum, while the cranium is not much larger than 

 that of Prozaedius, which it closely resembles. Unfortunately the only 

 available specimen is much mutilated, so that many of its features are quite 

 indeterminable. The cranium is short, broad and low ; the parietal emi- 

 nence is but slightly higher than the occipital crest, and thence the upper 

 profile descends very gradually to the end of the long rostrum. 



The occiput is low and very broad and has a moderately prominent 

 crest, the median dorsal portion of which is curved forward between the 

 parietals more abruptly and farther than in Prozaedius. The basiocci- 

 pital is broad, narrowing forward, with a median keel and shallow lateral 

 fossae ; the condyles are much as in the latter genus, but the external sul- 

 cus is far better defined. No sagittal crest is present and the sagittal 

 area is even more obscurely indicated than in Prozaedius. The glenoid 

 cavity differs from that of the latter in being narrower, more elongate and 

 of more oval shape. The frontals are marked by a postorbital constric- 

 tion, which is shallower and less abrupt than in the preceding genus, and 

 by an unusual preorbital extension ; apparently, the frontal sinuses pro- 

 duce hardly any convexity of the forehead. The nasals are narrow and 

 remarkably long ; anteriorly, they broaden somewhat, are bluntly pointed 

 and project well beyond the premaxillae, making the narial opening very 

 oblique. The premaxillaries are elongate and form most of the anterior 



