GLIRES OF THE SANTA CRUZ BEDS. 40 1 



convex, anterior face and near the mesial border are two faintly marked, 

 longitudinal grooves. 



NEOREOMYS VARIEGATUS Ameghino. 



(Plate LXV, Fig. 12.) 



Neoreomys variegatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pat- 



agonie, 1894, p. 68. 



The distinctive character of this species is to be found in p T , of which 

 the anterior prism has a well denned vertical groove on the outer side, a 

 feature which is not present in any of the other species. Size as in N. 

 australis. 



SCLEROMYS Ameghino. 



(Plate LXV, Figs. 13-15.) 



Scleromys Amegh. ; Enumeracion sistemat., etc., 1887, p. n. 

 Neoreomys Amegh. ; in part. 



This genus is much like the preceding one, from which it is distin- 

 guished by its smaller size and by the simpler pattern of the grinding 

 teeth. Individuals of Scleromys are quite rare and it is far less completely 

 known than Neoreomys ; not even a well preserved skull has yet been found 

 and the skeleton is entirely unknown. The incisors resemble those of 

 Neoreomys in character, but are slightly broader in proportion to the length 

 of the grinding series ; the anterior faces are more or less convex and have 

 a crepe-like surface, produced by faint, wavy longitudinal striations. The 

 upper grinding teeth are divided into two prisms by a deep internal fold, 

 which extends obliquely across the crown almost to the external wall ; on 

 more advanced wear the outer part of this fold is separated as a lake. A 

 second and much shallower fold invades the posterior prism from the 

 outer side, but is very early isolated as a lake. In advanced stages of 

 wear even the internal fold loses its connection with the peripheral enamel 

 and then the crown has three lakes, an anterior transverse pair formed 

 from the internal fold, and a posterior lake derived from the external fold. 

 In the lower teeth the pattern is, as usual, reversed, the principal enamel 

 fold being external and posterior, and the secondary fold internal and 

 posterior. 



So far as the skull is known, it is much like that of Neoreomys, with 

 certain characteristic differences. The parietal region of the cranium is 



