426 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



The nasals are long, narrow and of nearly uniform width, contracting 

 slightly in the middle, and anteriorly are strongly convex ; the free ends 

 are rounded and entire, with a deep notch between nasals and premaxil- 

 . laries. The latter are long and narrow, but of relatively large dorso- 

 ventral height ; between the alveolus of the incisor and the nasal is a thin, 

 triangular plate of bone, which is unusually large in this species. The 

 postorbital process of the frontal is but feebly developed. 

 The following dimensions are taken from No. 15,623: 



MEASUREMENTS. 



Upper dentition, length .............. 022 Lower incisor, width ................ ooi 5 



" " " pimi ........ 009 " " thickness ............. 002 



Upper incisor, width ................ 0015 Rostrum, length ................... 015 



" thickness ............. 0025 " width at base .............. 008 



Lower dentition, length ............. 020 " " " anterior end ........ 006 



0085 " dorso- ventral height ........ oio 



SCIAMYS VARIANS Ameghino. 



(Plate LXVII, Figs. 5-5*, 9.) 



Sciamys varians Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. 



This name may be applied to those skulls which approximate or equal 

 the preceding species in size, but differ from it decidedly in the shape of 

 the rostrum, which is broader, especially at the base, and more tapering 

 anteriorly, while the nasals are quite flat; the interorbital region also is 

 wider than in S. principalis and there appears to have been no post- 

 orbital process. 



The incisors are relatively narrower than in any other species of the 

 genus and in the upper jaw they have quite plane anterior faces, which 

 may or may not be marked by a very faint, hair-like groove. 



The remains of the skeleton, other than the skull, which may be re- 

 ferred to this species belong to a single individual (No. 15,168) and 

 consist of the cranium, mandible, two caudal vertebrae, parts of the humerus, 

 ulna, femur, the tibia, calcaneum, astragulus, metatarsal III and certain 

 phalanges of the pes. The description of the bones has already been 

 given in connection with the account of the genus, but attention should 

 be called to the relatively great length of metatarsal III, which exceeds 

 that of S. latidens. In the subjoined table the dimensions of the upper 

 teeth and skull are from No. 15,575, the others from No. 15,168. 



