32O PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



MEASUREMENTS. 



Lower dentition, length 032 T , width, left side 003 



" " " y_ T 025 3-, length 006 



Y length (i. e., antero-posterior diameter) " width oio 



right side 007 ^, length 006 



" width (z. e., transverse diameter) right " width 0105 



side 004 -f, length , 007 



T , length, left side 006 " width 0095 



PELECYODON BOMBIFRONS (Ameghino). 



Uranokyrtus bombifrons Amegh. ; Enum. Synopt. des Mamm. Foss. de 

 Patagonie, 1894, p. 160. 



The type and only known specimen of this species is the weathered 

 facial region of a skull, with all the teeth broken to the level of the alveoli. 

 Ameghino has referred it to a distinct genus because of the coossification of 

 the nasals and frontals, probably an abnormality. As a species, however, 

 it is quite well defined. In the dentition ^ is remarkably large and the 

 two series of upper teeth are not so nearly parallel as in the other species 

 of the genus, but converge posteriorly, making the palate more triangular 

 and more convex behind. 



The dimensions are taken from Ameghino's original description ("94", 



161). 



MEASUREMENTS. 



Upper dentition, length 038 , length 007 



i, length (/. e,, antero-posterior diameter) .007 " width 012 



" width (i. e., transverse diameter) 004 Palate, width at i 018 



i, length 008 " " " ^ 013 



" width 008 " " " - 6 007 



PLANOPSIDsE. 



This term is proposed instead of the name Prepotheriidce, which Ame- 

 ghino has employed ('94", 161), on account of the rule of nomenclature 

 which requires that the family name shall be taken from the genus first 

 described, and because of the grave doubt as to whether Prepotherinni is 

 not a synonym of Planops. There is some reason to believe that the 

 animals referred to this family may prove to be nearly related to the 

 Megatheriidcz, to which they have several suggestive resemblances, and in 

 that case, it would be advisable to incorporate them in the latter family, 

 though it would be premature and perhaps misleading, to do so without 

 fuller information. 



