l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



manner that the toothrow cannot be measured, but the alveolar length 

 must have been at least i8 mm. ; enough of the base of the rostrum is 

 preserved to show that the breadth at premaxillary suture was more 

 than 13 mm. In three mandibles from the same locality the toothrow 

 measures 17.6, 18.6 and 18.6 in contrast to the maximum of 17.2 for 

 the entire series of over 600 jaws from the Haitian caves. Of two 

 mandibles collected by Gabb at San Lorenzo Bay one has a toothrow 

 18.8 mm. in length, while in the other, an olwiously younger individual, 

 it is 16.8, only a little below the maximum for the Haitian specimens. 



APHJETREUS MONTANUS Miller 

 Plate 2, figs. 4, 4a, 4b 



Seventeen imperfect skulls and palates, 208 jaws. 



In both groups of caves the remains of this animal were common, 

 the frequency of their occurrence coming next after that of Isolobodon 

 levir. 



The material at hand makes it possible to define the genus more 

 completely than I was able to do in the original paper. It is now 

 evident that the genera Aphcctrcus, Isolobodon and Plagiodontia form 

 a rather compact group, the members of which are more nearly related 

 to each other than any one of them is to Capromys and its allies. In 

 all three the enamel pattern of the upper molars is tetramerous ; in 

 Plagiodontia the upper premolar has reached the same stage of simplifi- 

 cation, but in Aphcctrcus and Isolobodon this tooth retains a small 

 fifth element. The maxillary teeth of Capromys and Gcocaproiiiys are 

 all pentamerous. In the Isolobodon group the direction of the inner 

 reentrant fold is diagonally forward in the upper teeth, backward in 

 the lower teeth ; the reverse is the case in Capromys. The general 

 structiu'e of the crowns in the Capromys grou]) parallels that which 

 has been developed by the voles ; this is not true with regard to 

 Isolobodon and its allies. The characters of the three genera may be 

 tabulated as follows : 



Curve of upper incisor short, the root of the tooth lying at anterior 

 margin of zygomatic process of maxillary ; lower incisor terminating 

 beneath nn ; pm* with one outer reentrant angle, its enamel pattern 

 exactly similar to that of the molars ; reentrant folds in upper teeth 

 very oblique, their slant 45° or less as referred to corresponding 

 alveolar line ; reentrant folds on inner side of the lower teeth extend- 

 ing less than halfway across crowns; frontal sinus sufficiently inflated 

 to produce an obvious swelling over anterior zygomatic root, to en- 

 croach on area of antorbital foramen, and to a less degree on that of 

 orbit ; posterior margin of zygomatic process of maxillary lying about 

 in line with anterior alveolar border Plagiodontia. 



