22 
BULLETIN 51, UNITED STATES NATIONAL MUSEUM. 
■ 
Fig. 2.— Milk dentition 
of Eptesicus fuscus. 
No. 84550. x about 4. 
cation of incipient secondary cusps ( mp 2 of Pteroycon , cheek teeth of 
Phyllonycteris) . The presence of a definite secondary cusp below 
and behind the main cusp is probably characteristic of the loAver 
cheek teeth in the Vespertilionidse. It is very noticeable in Eptesi- 
cus fuscus , less so in Myotis albescens. Similar cusps occasionally, 
though less frequently, occur in the upper teeth and in both upper 
and lower canine ( Eptesicus (fig. 2), Myotis ). In Nyctinomus bra- 
siliensis the canine has an additional secondary 
cusp situated on the anterior edge of the tooth 
somewhat nearer the tip. Contrary to what might 
be expected, the milk incisors present more varia- 
tions of form than any of the other deciduous 
teeth. The simplest incisors are perhaps those of 
Desmodus , in which the upper teeth are of the 
primitive recurved type, without trace of second- 
ary curvature or extra cusps, while the lower teeth 
are widened above, the outer slightly bifid. In Nyctinomus brasilien- 
sis the upper incisors are simple and terete, but with a distinct double 
curve inward and backward, like those of Promops fosteri (fig. 3). 
The lower incisors are, however, much like those of the permanent 
set, with well differentiated, flattened, bifid crowns, the inner lobe dis- 
tinctly the larger. In Eptesicus and Myotis both upper and lower 
incisors are trifid, those of the lower jaw scarcely recurved and very 
closely resembling the teeth of the permanent set, those of the upper 
jaw strongly recurved and with the cusps longer and more distinct 
than in the mandibular teeth. In the three genera of Phyllostomidse 
at hand, Phyllostomus , Artibeus , and Phyllonyc- 
teris , there is evident differentiation between the 
inner and outer incisor of the upper jaw. This is 
slightest in Phyllostomus, where the outer tooth is 
longer than the inner, its point bent forward and 
th’en back, the concavity directed outward and 
backward; inner tooth with crown flattened but 
tapering to a fine recurved point below which there 
is a slight concavity on outer side. Lower incisors 
not seen. In Arbiteus the upper teeth are of much 
the same form, but the inner is distinctly notched at apex, much as 
in its successor; lower incisor faintly trifid, the middle lobe highest. 
Upper incisors of somewhat the same type are found in Phyllonyc- 
teris, though the differentiation is less evident. Inner tooth with a 
distinct secondary cusp on outer side considerably below level of main 
cusp. The lower teeth are so minute that the details of their form 
can not be determined. The upper incisors of Cynopterus and the 
Fig. 3.— Milk denti- 
tion of Promops fos- 
teri, Villa Rica, 
Paraguay. No. 
105681. x about 3. 
