412 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 



Upper dentition, length mi-m* 009 Skull, length condyle to premaxillary . .048 



Upper incisor, width 0015 Cranium, length to rim of orbit 031 



" " thickness 002 Face, length 017 



Lower dentition, length 024 Occiput, height on 



" " " Pf-my 013 Mandible, depth below p^ 008 



" " " m T -my oio 



SPANIOMYS MODESTUS Ameghino. 

 Spaniomys modestus Amegh. ; Enumeracion sistem., etc.; 1887, p. 10. 



This species, which is much less common than the preceding one, and 

 is known only from mandibles, is distinguished chiefly by its smaller size ; 

 the series of lower grinding teeth measures only 9 mm. in length and the 

 depth of the jaw below p T is only 5.5 mm. ; the anterior portion of the 

 mandible is lower, more slender and relatively more prolonged than in 

 S. riparius. 



SPANIOMYS BIPLICATUS Ameghino. 



(Plate LXV, Fig. 24.) 



Spaniomys biplicatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pat- 

 agonia, 1894, p. 70. 



A well-marked species, so distinct, indeed, that it may perhaps be 

 referable to a different genus. In size it is slightly smaller than the 

 average individual of S. riparius. The upper teeth are not known ; in 

 the lower teeth the anterior of the two external prisms, into which the 

 crown is divided by the broad and deep median enamel fold, is itself 

 subdivided by a vertical groove into two crests. The type specimen does 

 not make it clear whether this subdivision is present in all of the grinding 

 teeth, or only in my and -3. Length of lower grinding series = 1 1 mm. 



GRAPH IMYS Ameghino. 

 Graphimys Amegh. ; Rev. Argent, de Hist. Nat; T. 1,1891, p. 300. 



This genus, though known only from a single fragment of the mandible, 

 appears to be very distinct and carries the complexity of molar pattern in 

 this subfamily to its maximum. Like the other grinding teeth m^, has 

 on the inner side three enamel folds and four crests ; the additional fold 

 is produced by a groove subdividing the median crest, but differs from 

 the other folds and from the corresponding fold of the other teeth in being 

 much shallower and more widely open. 



