82 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



oblique ciugulc band (•institutes a marked peculiarity of this and allied 

 species. Both the central and lateral incisor are disposed to be turned 

 on themselves. The central presents its labial surface obliquely toward 

 the median line (see V\. x, tig. 8) ; the lateral at a right angle, orn early 

 so, to the central. The degree attained by this rotation constitutes the 

 difference between the divergence of the parallel alignment of the 

 main cusps. These peculiarities, according to Dobson, present char- 

 acters which are of value in distinguishing species. But they appear 

 to have no validity in American examples of Vespertilio. 



Canine with a well-developed concavity on pahital surtace, but with- 

 out any on the posterior surface. Its anterior surface is trenchantly 

 tinted near median border. Of the three premolars the tirst two are 

 small, conical with well-deiined cingula, the first with the larger. The 

 second is usually in tooth line, but may lie back of it, and therefore 

 not be seen fr(nn without. Molars have two supplemental lines ex- 

 tending from the commissure of the protocone to the apices of the sub- 

 equal Vs. Kudimeut of a heel is plainly discernible. The third molar 

 with a rudiment of a posterior limb. 



Mandibular teeth.— The first and second incisors crowded-trifid. The 

 third massive, square, or rugged, due to irregular development of the 

 cingulum, which nearly reaches the level of the obscurely trifid edge. 

 Canine with well-defined posterior and lingual surfaces. The first and 

 second premolars small, conical; the first the larger, the second some- 

 times thrown in a little of the axis of the series. The molars as m 

 Adelonycteris and Vesperngo; the heel of the third molar with small, 

 acute cusp. The cusps, seen from lingual aspect of the lower molars, 

 sharp and well developed. Tlie hypoconid slightly larger than the 

 triangle composed of the protoconid, paraconid, and metaconid. The 

 cino-ulum forms a little cusp on the posterior border of each molar. 



Bental variatwns.-ln a specimen from the mouth of the Colorado 

 Eiver (No. 11170, N. M.), the maxillary lateral incisor on both sides 

 was much larger than the small unicuspid central; the last line of the 

 second V of the third molar was absent. 



In the main modifications are noted in the relation of the superior 

 premolars and in the shapes of the superior lateral incisors. The pre- 

 molars may be crowded so that the second is often not visible from 

 without and even the first may be placed so far inside the line of the 

 other teeth as to be scarcely seen. Both Dobson and Merriam accept 

 this disposition as of specific significance. I can not concur. In ex- 

 amples of both V. gryphus and V. nitidus I find examples of this reces- 

 sion.* , , . T 



The cingulum of the lateral incisor may be entire or lacking on median 

 contour; the median flange may be crenulated or^mooth^^he^iahital 



of V. oiliolabrmn. 



