40 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



same teeth of Stenoderma as figured by Peters. Artibeus (Plate V, 

 fig. 1), shows the hypocone of m x large and in characteristic position 

 for the group — that is, mostly lingual to the protocone. In m 2 , how- 

 ever, the condition is about the same as in Uroderma. The genera 

 Ariteus, Phyllops, Ardops, and Sphceronycteris have the hypocone 

 of m 2 well developed and of the same form as that in m 1 , though not 

 as large. This is accompanied by an increased widening of the 

 crowns. The maximum of widening is seen in the first molar of 

 Oenturio (Plate VI, fig. 2), where the distance from hypocone to 

 protocone is nearly equal to that from protocone to paracone, and the 

 points of these three cusps are exactly in line with each other. 

 ■•Between the bases of the paracone and metacone in the first and- 

 second molar of Uroderma (Plate VI, fig. 1) may be detected a slight 

 depression, the middle of which is occupied by a faintly marked 

 groove. This is probably the first trace of the peculiar structure that 

 forms so conspicuous a feature in the second molar of each jaw in 

 E ctophylla. 



As already pointed out, a minute metaconule is present in Uroderma 

 and Stenoderma, apparently developed as a specialization of the 

 rugosity of the crushing surface. The same cusp is present in the first 

 and second molars of Brachyphylla (Plate VI, fig. 3) as a low though 

 evident longitudinal or oblique ridge, best developed in m 2 . In the 

 first molar there is a protoconule of somewhat the same size and form, 

 though smaller and more strictly longitudinal. This cusp becomes 

 of considerable importance in the second molar, where its height and 

 its basal area are both fully half as great as in the protocone, which 

 the new cusp resembles in form. So strong is this resemblance that 

 were it not for its position on the crown and for the reversal of the 

 relative sizes the protoconule might be mistaken for the protocone 

 and the protocone for the hypocone of a somewhat aberrant tooth 

 of the usual Stenodermine type. In the third molar a similar cusp 

 is present, though not as high or as well defined. The inner margin 

 of the teeth is without trace of cingulum or shelf-like rudiment of 

 the hypocone. In the mandicular teeth the intermediate cusps are 

 rather well developed in m ,, though absent or barely indicated in m t 

 and in m 3 . When present they assume the form of low, subterete 

 elevations at base of metaconid and entoconid. The very peculiar 

 arrangement of cusps in this otherwise primitive genus is probably 

 a development from a type in which the teeth resembled those of 

 Ghiroderma. 



The Pteropine dentition (Plates VII, VIII) though at first sight 

 strikingly different from that of the typical Microchiroptera, has 

 undoubtedly been developed from a primitive type similar to that 



a Monatsber. k. preuss. Akad. Wissensch., Berlin, 1876, plate facing p. 434. 



