4 PKOCEEDINGS OF THE NATIONAL MUSEUM vol. 72 



Pedro de Macoris and a series of six jaws which I collected in Haiti 

 in 1925. It is therefore to the species represented by these mandibles 

 rather than to the one collected by Doctor Abbott that I have decided 

 to apply the name sedium. If I am correct in so doing the original 

 Plagiodontia remains unknown in the living state. 



The characters of the two species, so far as it is now possible to 

 summarize them, may be contrasted as follows: 



Antero-posterier diameter of crown in mi and m2, measured along the median 

 axis of toothrow fully equal to and frequently greater than the transverse 

 diameter measured in line perpendicular to this axis; reentrant enamel folds rela- 

 tively wide and not excessively long; size larger: length of mandible to tip of 

 angular process in adults exceeding 60 mm., mandibular toothrow (alveoli) in 

 adults about 24 mm P. sedium 



Antero-posterior diameter of crown in mi, and m2, measured along the median 

 axis of toothrow distinctly less than transverse diameter measured in a line 

 perpendicular to this axis; reentrant enamel folds relatively narrow and long; 

 size smaller: maximum length of mandible to tip of angular process in adults 

 about 55 mm. or less, mandibular toothrow (alveoli) in adults less than 21 

 mm P. hylssum 



PLAGIODONTIA HYL^UM, new species 



Type. — Young-adult male (skin and skeleton) No. 239887, United 

 States National Museum. Collected at Guarabo, 10 miles east of 

 Jovero, Samana Province, Dominican Republic, November 23, 

 1923, by Dr. W. L. Abott. 



Characters. — General appearance essentially as in Plagiodontia 

 sedium but color probably darker and less yellowish, size slightly 

 less, and mandibular teeth with crowns compressed along the axis of 

 toothrow. 



External features. — In size and, external characters the animal is not 

 unlike Geocapromys hrowni of Jamaica, but the color is lighter and 

 more uniform, the entirely naked tail extends beyond the outstretched 

 hind feet by about one-fourth or one-third of its length, the ears are 

 so small as to be almost completely buried in the fur (in an adult 

 preserved in alcohol. No. 239898, the ear measures: height from 

 meatus 20, height from crown 12, width 12.6; the general depth of 

 the surrounding fur is about 19, with longest hairs 29), the feet are 

 heavier, with more robust, less curved claws, the claw on the thumb 

 is decidedly better developed, and the surfaces of the palms and soles 

 are less conspicuously and completely covered by minute tilelike 

 thickenings of epidermis, these rarely assuming the definite subcir- 

 cular or subpentagonal form which they commonly show in Geo- 

 capromys hrowni. A large area including the heel and much of the 

 postero-external region of the sole is nearly or quite smooth. The 

 tail is naked except that the fur of the body extends out on its extreme 

 base for a distance of about 10 mm., and the rest of its surface is 

 sprinkled with minute hairs (about 2 mm. in length) so sparsely 



