44 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 



crest is very prominent and quite thick. The basioccipital is broad 

 behind, narrowing forward ; its hinder end is broadly, but not very deeply 

 notched by the foramen magnum, which is very large. The condyles are 

 of semicylindrical shape, sessile and transverse. No paroccipital processes 

 are present, but the mastoid portion of the periotic, which is quite exten- 

 sively exposed on the surface, ends in a short, heavy mastoid process. The 

 tympanic, which was very loosely attached, is a small, incomplete ring of 

 bone, with large, irregular external meatus. The parietals are relatively 

 short and hardly form so much of the cranial roof as in Dasypus and they 

 carry a low, but very distinct sagittal crest, which is much better defined 

 than in the allied species. On each side of the crest is a narrow and 

 smooth sagittal area, thus producing a characteristic triple appearance. 

 This area is quite broad at the junction with the occipital crest, narrows 

 rapidly and then broadens again gradually to the coronal suture. Along 

 the squamosal sutures the parietals are perforated by a number of conspicu- 

 ous venous foramina and their surface is generally rough. 



The squamosal is long, but low, forming relatively little of the cranial 

 wall ; the portion ventral to the glenoid cavity and external to the tym- 

 panic has an inflated appearance, as though it were involved in the forma- 

 tion of the auditory bulla. The glenoid cavity proper is a slightly convex 

 surface, most of which is placed upon the ventral side of the zygomatic 

 process, but internal to this is a deep, longitudinal groove, ending pos- 

 teriorly in a deep fossa, at the bottom of which the glenoid foramen 

 opens ; there is no definite postglenoid process, the fossa abutting against 

 the posttympanic process. The zygomatic process has much the same 

 shape as in Dasypus, but its dorsal surface is somewhat more concave 

 and it does not extend so far over the jugal. The latter is rather short ; 

 its posterior half is laterally compressed and slender, while the anterior half 

 is expanded into a great vertical plate, which together with the zygomatic 

 process of the maxillary, forms a large, anteriorly presenting, suborbital 

 process, like that of the glyptodonts on a much smaller scale. As a 

 whole, the zygomatic arch pursues a course like that of Dasypus, curving 

 downward and forward. 



The lachrymal has a fairly large facial portion, which contracts to a point 

 anteriorly; the foramen is small and placed within the rim of the orbit. 

 The frontals are large and together have an hour-glass shape, with deep 

 postorbital constriction, in front of which they expand more widely than 



