22 



BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



Pig. 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 lower 

 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 Phyllostomidae 

 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 

 then 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 PBOMOFS FOS- 

 TERI, Villa Rica, 

 Paraguay. No. 

 105681. x about 3. 



