ART. 16 THE GENUS PLAGIODONTIA MTLLEK 7 



first and second salient folds on the lingual side of the teeth are 

 usually truncate at the tip in Plagiodontia liylseum, while in P. 

 aedivm a lanceolate termination for all three folds appears to be 

 normal, though the material is not in sufficiently good condition to 

 show this is a reliable diagnostic character. In both species the 

 enamel margin of the cheekteeth becomes thin and nearly or quite 

 discontinuous for a varying distance along the anterior apex of 

 pm4 and along the anterior border of each of the molars in the region 

 of its contact with the tooth in front of it. This process appears to 

 be more pronounced in P. hylseum than in P. sedium. 



No satisfactory comparison of the maxillary teeth with those of 

 P. sedium is now possible. 



Measurements. — For measurements, see accompanying table. 

 "Head and body" and "tail" were measured by the collector. The 

 "hind foot" includes the claws. All specimens with complete meas- 

 urements are from Guarabo, Dominican Republic. 



Remarks. — The series of ten adult skins is very uniform, such 

 individual variation as occurs on the dorsal surface being confined 

 to slight differences in the yellowness of the wood-brown element of 

 the color, and to the greater or less abundance of dark tipped hairs 

 on the back and sides. Ventraliy there is slight variation in the 

 tone of the buffy-brown, this assuming a faint drabby cast in some 

 of the skins. An immature individual (No. 239894) is more grayish 

 than the adults, but the difference is not conspicuous. The skulls 

 and teeth are equally constant in all their characters. Perhaps the 

 two most variable features of the skull are the exact size and form 

 of the frontal swellings over the sinuses, and the outline, broadly or 

 narrowly triangular or occasionally peglike, of the postorbital proc- 

 esses. The enamel pattern is very constant and is apparently not 

 subject to variations due to age. 



