250 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



MEASUREMENTS. 



Type. No. 15,525. No. 15,529. 



Upper dentition, length .037 



" " " 1-A 023 .022 -0235 



1, length (i. t., antero-posterior diameter) .006 



" width (/. e., transverse diameter) : .004 



1, length .005 .005 



"width .006 .0055 



3, length .0055 .0055 



" width .0065 .007 



A, length .0045 .005 



" width .006 .0065 



i, length .003 .003 5 



" width 004 .005 .005 



In appearance and proportions the skull is one of the most peculiar to 

 be found in the present genus and the peculiarities are best displayed in 

 the Killik Aike specimen (No. 15,529), (Plate XLIV, fig. 2). The occi- 

 put is both broad and high and the cranium is strongly vaulted ; from the 

 parietal eminence, which is longer than usual and extends forward to the 

 frontal suture, there is a steep descent forward to the forehead and thence 

 a very slight descent to the end of the rostrum ; the contrast in dorso- 

 ventral height between the cranial and facial regions is thus very marked. 

 An occipital crest can hardly be said to exist, and the sagittal crest is 

 either entirely absent (No. 15,525) or very feebly indicated on the frontals 

 only (No. 15,529), in which case it is associated with a sagittal area on 

 the parietals ; the supraoccipital is very extensively reflected over upon the 

 dorsal surface of the cranium, especially in the Lake Pueyrredon specimen. 

 The parietals form more of the cranial walls than usual, while the squa- 

 mosals are relatively small ; the frontals have less of an hour-glass shape 

 than in most species of the genus, for the expansion in front of the post- 

 orbital constriction is slight and very gradual. The maxillaries have no 

 especially characteristic features except the small size of the preorbital fossae 

 and the flatness of the palate. 



MEASUREMENTS. 



No. 15,525. No. 15,529. 



Skull, length from foramen magnum to anterior nares ?. 106 



Cranium, length from foramen magnum to edge of orbit 087 .084 



Face, length orbit to anterior nares P.O22 



Occiput, height 036 .032 



" width at base 043 043 



