38 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



dibular molars retain all of their cusps, but these are low and 

 rounded. This is especially true of the paraconid, which is much the 

 lowest of the cusps on inner side. The protoconid and metaconid, as 

 well at the hypoconid and entoconid, stand nearly opposite each other, 

 the anterior pair united by a rather high ridge, the remnant of the 

 second commissure. 



Another stage is represented by the Sturnirinse (Plates III, IV, fig. 

 3). Here the styles and commissures have completely disappeared, 

 leaving a parallel-sided, squarish, or oblong crown, the median por- 

 tion of which is occupied by a broad groove nearly continuous from 

 one tooth to the next. In the upper teeth the three primitive cusps 

 are present and in practically their normal position, though all are 

 much hollowed out from the inner side. The protocone is large, ex- 

 tending along entire lingual side of tooth. Paracone smaller, but 

 better defined than metacone. Third molar with the elements so 

 reduced that the homologies of the cusps are doubtful. In the lower 

 teeth the reduction of the paraconid, begun in the. Glassophaginse, is 

 carried so far that this cusp is absent in m 2 and m 3 , while in m ± it is 

 decidedly the smallest of those on lingual side. The other cusps 

 stand opposite each other in pairs, the metaconid facing the proto- 

 conid and the entoconid facing the hypoconid. They are of much 

 the same character as those of the upper teeth, being placed at ex- 

 treme edge of crown and with the inner side hollowed out to form 

 the longitudinal furrow. Traces of the four principal cusps are 

 visible in the posterior tooth. 



In the typical genus of Phyllonycterinse (Plates III, IV, fig. 4) a 

 stage is reached in which the lower molars closely resemble those of the 

 Pteropidse, while the upper teeth remain more as in the Sturnirinse. 

 From those of the latter group the maxillary teeth differ, principally 

 in the lowering of the protocone, so that the longitudinal groove 

 becomes rather a broad, nearly flat, crushing surface. The paracone 

 and metacone are also flattened, but their distinctness remains evi- 

 dent. In the slight hollow between them may often be seen the last 

 trace of the mesostyle (not shown in the figure). In the mandible 

 the crowns of the molars are flat, with a slightly raised rim, on 

 which is faintly indicated a trace of the protoconid, metaconid, and 

 hypoconid. So faint are these traces that they might readily escape 

 notice. In m j the anterior portion of the crown is somewhat nar- 

 rowed, bearing a rather prominent cusp, probably the protoconid, on 

 the anterior inner side of which there is a slight concavity. This hol- 

 low may represent the space between protoconid and paraconid. A 

 glance at fig. 4, Plate IV and Plate VIII, will show the striking simi- 

 larity between these teeth and those of the Pteropidse. Before pass- 

 ing to the latter, however, it may be well to describe a very important 

 aberrant type of crushing dentition found in the Phyllostomidse. 



