4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 66 



teeth based on the Acaremys plan, while Plagiodontia and Isolobodon 

 have teeth with the same underlying structure as those of Scleromys 

 (Santa Cruz), a type which recurs in the living Ahrocoma and cer- 

 tain species now placed in Proechimys. Except that Capromys is 

 represented on the mainland by the slightly different Procapromys 

 of Venezuela, these three living genera stand alone as compared 

 with all the nearly-related South American hystricines, both living 

 and fossil, in their complete attainment of ever-growing teeth. 



So far as can be judged from eight very distinct genera the 

 Antillean hystricine rodents do not present the characters that would 

 be expected in animals derived from South America during any 

 period geologically recent. Neither have they the appearance of 

 an assemblage brought together at different times by migration or 

 chance introduction. On the contrary they suggest direct descent 

 from such a part of a general South American fauna, probably not 

 less ancient than that of the Miocene, as might have been isolated by 

 a splitting off of the archipelago from the mainland. Of later 

 influence from the continent there is no trace. 



CANID. Species? 



The left mandible of a canid with pm,, pm^ and pm^ in place 

 (No. 217139, U. S. Nat. Mus.) is among the specimens in the Cuban 

 collection. It differ^ from the jaws of such Indian dogs as I have 

 seen (both North American and South American) in the unusual 

 width of the premolars and the complete absence of secondary cusps 

 on all three of these teeth. A toothless left maxilla (No. 217130) 

 from the same locality closely resembles the maxilla of a domestic 

 dog's skull from pre-Columbian deposits near Lomas, Peru (No. 

 176386). 



CAPROMYS PILORIDES (Say) 



Represented by numerous skulls and leg bones from Big Wall. 



CAPROMYS PREHENSILIS Poeppig 



A right mandible and left femur from Big Wall are probably 

 referable to this species. 



ISOLOBODON PORTORICENSIS Allen 



(Plate I, fig. 3) 



Macoris: 207 specimens (representing probably about 40 indi- 

 viduals) : palate i ; lower jaw (right) 5, (left) 11 ; auditory bulla, 

 I ; odd cheek teeth (mandibular) 22; lower incisor i ; scapula (left) 



