4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 62 



American relatives. The upper incisors are more abruptly curved and 

 their course is slightly if at all evident on the side of the rostrum or 

 in the antorbital foramen. Similarly the shaft of the lower incisor is 

 less conspicuous on the under side of the mandible; its base does not 

 extend quite so far beyond the root of m. as in the case of Proechiinys. 

 All the maxillary cheekteeth are 3-rooted as in ProccJiiinys, but the 

 inner root is merely larger than either of the others and not specialized 

 in form as it is in the South American animal. In both genera the 

 mandibular teeth are 3-rooted w^ith the exception of the 2-rooted 

 premolar. The large root is placed behind and the two small roots 

 in front. 



The enamel pattern is less complicated than that of Proechiinys 

 semispinosns. In all of the teeth except pm^ the pattern is unmodified 

 pentamerous with the two reentrant folds of the paramere slightly 

 deeper than the single reentrant of the protomere. In the lower pre- 

 molar the protomere bears a shallow second reentrant fold near the 

 front of the crown. This fold is so shallow that it is soon cut off as an 

 enamel lake. No species of Proechiinys that I have seen is as simple 

 as this in its enamel folding. The fundamental conditions present 

 in Brotomys are, however, exactly reproduced in Cercoiiiys, though in 

 this South American genus there is a slight specialization in the form 

 of a peripheral narrowing of the reentrant folds of the metamere 

 which causes these folds to become early isolated as lakes. 



PLAGIODONTIA HYLJEUM Miller 



Right mandible (no teeth), i ; left auditory bulla, i ; fragment of 

 ulna, I ; fragments of innominates, 2 ; femur, i ; tibia, i ; epiphysis 

 from head of tibia, i ; astragalus, i ; calcaneum, i. 



PLAGIODONTIA sp. ? 



A first or second upper molar, a first or second lower molar, and 

 three separate plates of a larger tooth, apparently nii or nio, suggest 

 the occurrence of a Plagiodontia with teeth more compressed antero- 

 posteriorly than they are in any of the three species now recognized. 

 Two auditory bullae slightly dift'erent from those of P. hylccuiu may 

 pertain to this animal. 



ISOLOBODON LEVIR Miller 



Probably two individuals, both immature, represented l)y the left 

 half of a palate and three loose teeth. 



