256 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 



MEASUREMENTS. 



No. 15,564.. No. 15,534.. No - J 5,5 22 - 



Upper dentition, length 044 



3.-A 026 .025 .026 



1, length (i. e., antero-posterior diameter) 007 



" width (/'. e., transverse diameter) 0065 



i, length 0055 .005 .0055 



" width 007 .0065 .008 



i, length - 006 .006 .005 



" width 0085 .008 .0085 



A, length 005 .005 .005 



" width 008 .008 .007 



, length 003 .0035 .004 



" width .006 .006 .007 



The following measurements are from the type-specimen, No. 15,564. 



Lower dentition, length 036 ^, width 008 



j_ 022 3, length 006 



T , length 006 " width 008 



" width 005 T , length 0075 



j, length 0053 " width 007 



The general characters of the skull have been given in the diagnosis 

 of the species and it remains only to mention some of the more important 

 details. The occiput is unusually low and wide, and is nearly vertical, 

 with a broad median convexity, which is especially distinct in the fully 

 mature individual ; near the dorsal border of this convexity appears a 

 median ridge, which extends for a short distance upon the dorsal side of 

 the cranium ; the foramen magnum is small, as are also the nearly sessile 

 condyles ; no paroccipital processes are apparent. 



The occipital crest is weakly developed, dying away dorsally, but be- 

 comes more distinct with age ; the supraoccipital is reflected upon the 

 dorsal side of the cranium to an unusual degree, much less, however, in 

 No. 15,522, which is the most aberrant of the series and may pertain to 

 another species. The broad, vaulted parietals show no trace of a sagittal 

 crest and only an obscurely indicated sagittal area. The forehead is 

 broad and nearly flat and the postorbital constriction is very shallow ; the 

 sagittal crest is absent from the frontals of all but the oldest individual, 

 in which it is feebly developed. The nasals are very wide, especially at 

 the hinder end, where they describe the segment of a circle, quite deeply 



