226 BULLETIN" 51 , UNITED STATES NATIONAL MUSEUM. 
Type-species. — Histiotus maculatus J. A. Allen. 
Geographic distribution. — Southwestern United States. 
Number of forms. — The type species is the only member of the 
genus thus far discovered. 
Characters. — Dental formula : 
-2 3. 1. - 2- 4567 .2-2 1-1 2-2 3-3 
1 2 3. 1. - 2 - 4 5 6 7 1 3 - 3’ c 1 - 1’ ' pm 2 - 2’ m 3 - 3“ 34 ' 
Upper incisors alike in form, slender, with well-developed cingula, 
and simple, styliform crowns, the outer somewhat larger than inner, 
which is in contact or nearly so with canine ; lower incisors trifid, the 
middle lobe largest, especially in i 2 and { 3 . Upper canine small and 
weak, barely more than twice the height of inner incisor, which it 
rather closely resembles in form; lower canine relatively smaller 
than in any other known Vespertilionine 
bat, its crown scarcely higher than that of 
pm 4 and not as high as protoconid of m 3 
or m 2 , with a noticeable posterior heel ris- 
ing at edge to a distinct cusp, and a large 
secondary cusp anteriorly rising above 
crown of outer incisor, and giving the 
tooth when viewed from the side and 
slightly in front an unequally bilobed ap- 
pearance unique so far as I have seen in the 
order. Anterior upper premolar minute, 
scarcely more than one-third as large as 
Fig. 37. — euderma macula™, outer incisor and rising barely to cingulum 
adult male, mesilla park, 0 f can ine. It stands in the tooth row at 
New Mexico. No. 122545. xl|. 
the middle or the narrow space between 
canine and large premolar, and in form resembles the incisors, except 
that the crown is relatively lower and thicker ; large premolar of the 
usual form, but very deeply concave on anterior border; lower pre- 
molars of the ordinary Vespertilionine type. Molars normal; m 1 
and m 2 with barely indicated hypocone, and with protocone sepa- 
rated from outer cusps by a rather unusually wide space, para- 
cone and metacone high and slender, mesostyle rather short but W 
pattern very distinct; m 3 with, well-developed metacone and three 
commissures, the area of its crown fully half that of either of the 
other molars; lower molars with all the cusps unusually high and 
slender, especially the protoconids, which considerably exceed the 
hypoconids; a distinct though low cingulum cusp behind the ento- 
conid in each tooth. Skull (fig. 37) with large, rounded, though 
rather low brain case and excessively weak rostrum; zygomata 
abruptly expanded at middle; audital bullse very large, and much 
