1892.] NATURAL SCIENCES OF PHILADELPHIA. 173 



named appears to take the place by adaptation of the region of the 

 hypocone. 



A recent observation on Cephalotes has suggested to the recorder 

 that it is probable that the hypocone is really present and that the 

 greater part of the grinding surface may be so named. In this 

 genus the parts protocone, ])aracone and metacone can be easily 

 discerned. The protocone according to this identification compels 

 one to accept the cusp named as protocone as in truth the metacone, 

 and thus the usual elements of a tritubercular tooth are all accounted 

 for, and the remaining extended part of the tooth becomes the 

 hypocone. 



By this identification the pteropine molar ceases to be aberrant. 

 But it must be remembered that tlie process of reduction of the 

 face which takes place in the pteropines is likely to be accompanied 

 with the same disposition to tooth variation as is seen in the Steno- 

 derms among the Phyllostomidce. In this family the molar teeth 

 are highly aberrant and the commissures at the anterior and pos- 

 terior borders greatly developed. The question naturally arises why 

 may not the molar in Cephalotes be acknowledged to be also aberrant 

 and the cusp named above the protocone be in reality nothing but 

 a supplemental cusp projected from the anterior commissure and the 

 parts as defined for the long faced Pterojms be true for all genera ? 

 On the whole Dr. Allen inclined to the opinion that the statement 

 first made was the correct one since it permitted the cusj^s to be 

 named with the least amount of violence to accepted views. 



The first molar in both Cephalotes and the related Harpyia 

 closely resembles the last premolar, so closely indeed as to suggest 

 that it may prove to be one of the premolar series. But our knowl- 

 edge of the milk dentition does not permit this identification to be 

 made with certainty. The transition in all the details is certainly 

 much more gradual than is usually the case between a molar and a 

 premolar. In Harpyia at least the first molar as defined in accepted 

 descriptions lies under and slightly in advance of the infra orbital 

 foramen, a remarkable position for it when the greatly reduced 

 facial axis is borne in mind. 



A striking peculiarity is seen in the last upper premolar and both 

 upper molars of Cephalotes in the presence of a longitudinal ridge 

 on the grinding surface of the tooth back of the paracone. The 

 ridge lies in the middle of the tooth. It is rudimental in the pre- 

 molar and the last molar but is trenchant in the first molar. 



In the lower jaw' of Cephalotes the teeth present similar 

 peculiarities to those of the upper with the exception that the longitu- 

 dinal ridge is absent from the last premolar, is rudimental in the 

 first and last molar but well developed in the 'second. The single 

 specimen of Cephalotes examined was a young adult and the pre- 

 maxillaries were united. 



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