GLIRES OF THE SANTA CRUZ BEDS. 479 



EOCARDIA DIVISA (Ameghino). 



(Plate LXVIII, Fig. 24.) 



Eocardia divisa Amegh. ; Enumeracion sistem., etc., 1887, p. 13. 

 Tricardia divisa Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 302. 

 Tricardia crassidens Amegh. ; Ibid., p. 303. 



The type of this species I have not seen and am therefore unable to 

 speak confidently of its status. It is the largest known representative of 

 the genus, the lower grinding series being 23 mm. in length. The lower 

 incisor is somewhat longer than in E. montana and extends to nvj. P T 

 appears to be constantly divided into three external crests, the anterior 

 one of which may become a small, subcircular pillar. 



SCHISTOMYS Ameghino. 



(Plates LXVIII, Figs. 26-26"; LXIX, n-i8 6 .) 



Schistomys Amegh. ; Enumeracion sistem., etc., 1887, p. 13. 



Eocardia Amegh.; in part; Rev. Argent, de Hist. Nat., T. I, 1891, 



P- 145- 

 Procardia Amegh. (subgenus) ; Ibid., p. 302. 



Procardia Amegh. (genus) ; Enum. Synopt. des Mamm. Foss. de Pata- 



gonie, 1894, p. 73. 



This very well marked and distinct genus is closely allied to Eocardia, 

 but with several important differences, which may be noted in all parts of 

 the skeleton. The incisors tend to be heavier, though the difference is 

 not striking; p- (Plate LXIX, fig. i i d ] is molariform and is composed of 

 two triangular prisms, which are a little thicker and separated by a some- 

 what shallower valley than in the molars ; m^ is decidedly variable in 

 form and in the size of its posterior process, which is straighter and less 

 incurved than in Eocardia. In the unworn teeth the three external valleys 

 are present, just as in the latter genus, and are soon isolated by wear as 

 enamel lakes and then disappear altogether. All the upper grinding 

 teeth are more strongly curved than in Eocardia, so that the masticating 

 surfaces present more obliquely outward. The two dental series converge 

 forward somewhat more strongly than in the latter, and their grinding 

 surfaces have a forward and downward inclination, which is almost as 

 decided as in Dolichotis. 



