3IO PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. 



MEASUREMENTS. 



Type. L. P. Museum. No. 1^,04.9. No^ 



A, length 007 .007 .006 



" width 006 .0063 .005 3 



, length 0053 .005 .006 .0053 



" width 0083 .008 .009 .008 



A, length 005 .005 .006 .005 



" width 0073 .0065 .0085 .0065 



*, length 003 .0025 .0043 .0033 



" width 007 .005 .0073 .007 



Type. No. 2. Type of P. robustus. 



Lower dentition, length 028 .026 .027 



" " " j_ ? 022 .020 .021 



T , length 006 .007 -0055 



" width 002 .003 5 .004 



j, length 006 .005 -0055 



" width 009 .008 .009 



j, length 007 .005 .0065 



" width 009 .007 .010 



T , length 007 .0065 .0065 



" width 008 .005 $ .008 



In specimens that have not been distorted by pressure the profile of the 

 skull resembles that of Schismotherium splendens, the upper contour rising 

 even more steeply to the parietal eminence and thence descending gently 

 and uninterrupedly to the end of the rostrum ; the occiput is low, inclined 

 slightly forward, and convex, save in the median dorsal region, where it 

 becomes slightly concave, though very much less than in Schismotheritim 

 and hardly at all in some specimens ; the median vertical ridge which 

 runs from the occipital crest nearly to the foramen magnum is much 

 more prominent in some individuals than in others ; the occipital crest is 

 well defined, but very variable in degree of prominence ; the foramen 

 magnum is small and subcircular, and the condyles are small, sessile, 

 and projecting little behind or below the occiput ; the fossa between the 

 exoccipital and squamosal is much deeper than in Schismotherium. The 

 tympanic is of the usual type, a loosely attached, incomplete ring. 



The parietals differ little in their proportions from those of Schismo- 

 therium splendens ;. the sagittal crest is usually a thin ridge, but in the 

 type-specimen its posterior portion is a narrow area, as in the last named 

 species ; the crest is continued for a considerable distance upon the fron- 

 tals, dividing into faintly marked temporal ridges, which are even more 



