66 



PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



So far as they are known, the vertebrae do not differ except in size, 

 from those of the other species. The caudals (Plate XIII, fig. 7) are very 

 scantily represented in any of the specimens referable to this species or 

 even to the genus. It is evident, however, that the tail was not unlike 

 that of Dasypns and altogether different from that of Stegotherium. In 

 the more anterior part of the tail the vertebrae have very short, but very 

 broad and heavy and slightly amphiccelous centra, very small neural canal, 

 but well-developed arches and zygapophyses and long, slender transverse 

 processes. These are succeeded by a number of vertebrae, which have 

 centra of nearly the same length, but much narrower and more depressed, 

 with only rudiments of the various processes, and growing gradually 

 smaller towards the end of the tail. 



The only available specimen of the pelvis of this species displays certain 

 peculiarities, but it is very difficult to say how far they are due to crushing. 

 The gluteal surface of the ilium is small and quite concave ; the acetabu- 

 lar border presents externally, giving the iliac surface an oblique position, 

 almost as much ventral as lateral ; the ilio-pectineal process is better de- 

 veloped than in P. robustus. 



The thigh-, leg- and foot-bones (Plates XV, figs.' 7, 8 ; XIV, fig. 7) 

 differ in no significant manner from those of the preceding species. 



The dimensions given in the table below are from a specimen (No. 

 15,613), which includes a part of the carapace, the skull and mandible, 

 the lumbar vertebrae and the anterior part of the sacrum and pelvis ; it 

 was collected by Mr. Peterson near Coy Inlet. 



MEASUREMENTS. 



Upper dentition, length 0495 



l-A 0225 



Lower dentition, length 05 1 5 



T _ T 017 



Skull, length on median basal line (ca.) .106 



" greatest length (ca.) .127 



Cranium, length to anterior rim of 



orbit 055 



Cranium, width at zygomatic processes .044 



Occiput, height 035 



" width at base 040 



" " across condyles 037 



Forehead, width 052 



Face, length. (ca.) .071 



Mandible, length of symphysis. . .(ca.) .022 



" depth below T 015 



" thickness below y 0095 



" width of ascending ramus . . .025 



'' height of condyle 040 



Last thoracic, length of centrum 013 



" " width of posterior face . .023 



" " height of neural spine . . .042 



width over metapophyses .054 



First lumbar, length of centrum 014 



" " width of posterior face. .022 



height of neural spine . . .044 



