ALLEN: NEW FOSSIL MAMMALS FROM CUBA. 7 



guishing Boromys from Brotomys. In the tooth pattern, however, 

 the type specimen seems to correspond more nearly to the description 

 of Boromys, to which T sliall provisionally refer it. 



The essential feature of the molars in both genera is probably the 

 same, though Boromys, so far as at present known, seems to have 

 deeper anterior secondary folds of the enamel. The upper molars 

 have each a deep median enamel fold on the inner and the outer side, 

 that meet at the middle of the tooth. The anterior half has another 

 fold from the exterior, which though extending a trifle beyond the 

 median line of the tooth, is of less vertical extent than the primary 

 fold. The posterior half has a similar secondar;^' fold extending inward 

 from the palatal side of the tooth. As Miller points out, the posterior 

 secondary fold is smaller than the anterior, so that the minute enamel 

 lake to which it eventually is reduced by wear, disappears before the 

 anterior la.ke, a condition which appears to obtain in the type here 

 described. In this specimen the second molariform tooth, m}, is more 

 worn than the first, pm'^, so that it has a large lake of enamel in its 

 anterior half and a smaller round one in its posterior, whereas pm* 

 has the anterior secondary fold still strongly connected with the 

 external enamel wall, while the posterior secondary fold is reduced to a 

 small roimd dot. Both these upper teeth are slightly everted. In 

 the empty alveoli, the cavities of three roots are seen, two anterior, 

 and a third posterior occupying the breadth of the cavity. The ante- 

 rior edge of pm^ is on a level with the posterior edge of the zygomatic 

 root. 



In addition to the type palate, several lower jaws were found, which 

 though dissociated, unquestionably belong to this species. All are 

 of uniform size. The lower incisor is strong, its base curving back 

 and out, to end slightly above and external to the alveolar row of the 

 molars. Its anterior enamel face is orange-yellow in color, in contrast 

 to the very shining white of the molars. As in the upper molars the 

 outer median enamel fold (Plate, fig. 11) has its tip very slightly 

 posterior to that of the irmer fold. A minute round enamel lake is 

 present in both anterior and posterior halves of the first tooth, pvii, 

 but in the posterior half only of the two succeeding teeth, nii and mo. 

 In this respect the lower molars dift'er from those of Steiromys, which 

 has a secondary reentrant in the anterior lobe of the molars. None 

 of the specimens shows 1113 in place. Two isolated teeth, evidently 

 lower molars, show clearly that there is no secondary reentrant in the 

 anterior half, but that it is present in the posterior half only (Plate 

 fig. 12). 



