GLIRES OF THE SANTA CRUZ BEDS. 449 



Unfortunately, I have seen no example of this remarkable species and 

 therefore merely translate Ameghino's descriptions in somewhat abbreviated 

 form. 



"Molars formed by two laminae, separated by a groove and united at 

 one end, as in Perimys, but more compressed and the laminae not placed 

 in complete juxtaposition, but obliquely for only one-half or one-third of 

 the width and with perpendicular, enamel-free bands" ('87*, 12). 



" The lower molars measure 4 mm. in width by 9 mm. in length ; they 

 are implanted more obliquely than in any of the other genera, so much so 

 that they may be said to be placed with their major diameter in almost 

 the same direction as the long axis of the jaw and in such a way that the 

 succeeding molar is placed with its antero-internal border against the 

 postero-external border of the tooth in front of it" ('89*, 170; PI. VII, 

 figs. 23, 24). 



"Size considerable, larger than Lagostomus trichodactylus. Upper molars 

 of the same type as in Perimys, but implanted much more obliquely to the 

 long axis of the jaw and more compressed antero-posteriorly " ('91*, 143). 



The following species are represented by such incomplete materials as 

 to permit of no satisfactory determination of their validity. 



PERIMYS PLANARIS Ameghino. 



Perimys planaris Amegh. ; Rev. Argent, de Hist. Nat; T. I, 1891, p. 



144. 

 Perimys planaris Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- 



gonie; 1894, p. 71. 

 Perimys planaris Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 



1898, p. 179. 



PERIMYS ANGULATUS Ameghino. 



Perimys angulatus Amegh.; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 



301. 

 Perimys angulatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- 



gonie, 1894, p. 72. 

 Perimys angulatus Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 



1898, p. 179. 



