THE FAMILIES AND GENERA OF BATS. 
241 
is distinctly greater than their length. Canines well developed, not 
peculiar in form, the lower approximated posteriorly, though not in 
contact, the antero-inner edge with distinct convexity just above level 
of incisors, the posterior base with small rounded, median cusp. 
Upper premolars well developed, the anterior (pm 2 ) very slightly 
smaller than posterior (pm 4 ) and closely approximating it in form, 
the posterior tooth with distinct antero-internal cusp, lower premolars 
large, the anterior ( pm 2 ) not as high as posterior (pm 4 ) but fully 
equal to it in cross section of base ; each tooth has a rounded postero- 
basal cusp much like that of lower canine. Molars normal ; m 1 and 
m 2 with inner segment deeply divided from outer, its inner border 
squarely truncate, the protocone rather low but long, its commissure 
abruptly bent downward posteriorly at a point corresponding to the 
usual position of the hypocone when present, but with no other dis- 
tinct trace of hypocone; a narrow but evident postero-internal heel 
present in both teeth, but particularly well developed in m 1 ; third 
upper molar with large metacone and third commissure ; lower molars 
with all the cusps present and of the usual form, though rather low 
and thick ; pm 3 with distinct entoconid. Skull in general appear- 
ance not unlike that of Myotis myotis , but somewhat smaller, dis- 
tinctly narrower, and with much shorter, almost uniformly convex; 
zygomata. Posterior opening of antorbital canal essentially as in 
Natalus , occupying practically the entire anterior wall of orbit and 
extending upward to and including region occupied in Myotis by the 
lachrymal foramen which here does not exist as a separate orifice; 
anterior opening of canal larger than in Myotis , but not extraordi- 
narily so. Foramen rotundum very large, coalesced with optic fora- 
men, the aperture broadest and squarely truncate anteriorly, where 
breadth is about equal to that of interptergoid space. Palate slightly 
concave both laterally and antero-posteriorly, the anterior portion 
entire except for two minute lateral foramina ; pterygoids parallel. 
Basiphenoid pits barely indicated. Audital bullse essentially as in 
Myotis myotis , but not as large. Mandible differing conspicuously 
from that of Myotis in the low coronoid (not exceeding articular 
process in height) and short angular process. 
Species examined. — Mystacops tuber culatus (Gray). 
Family MOLOSSID^B. 
1821. N octilionidw (part; Race 1, part) Gray, London Medical Repository, 
XV, p. 299, April, 1821. 
1827. Vespertilionina Lesson, Man. de Mammalogie, p. 99 (part). 
1831. Vespertiliones ( Vespertilionid(r ) (part: Noctilionina, part) Bona- 
parte, Saggio di una distrib. metodica degli Anim. Vert., p. 14. 
1838. V espertilionidcc (part; Noctilionina, part) Bonaparte, Nuovi Annali 
delle Scienze Naturali, Bologna, Anno I, Tomo II, p. 112, 
25733 — No. 57 — 07 m 
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