NO. I LOWER EOCENE MAMMALIAN FAUNAS — GAZIN TJ 



ISECTOLOPHIDAE 



HOMOGALAX PRIMAEVUS (Wortman) 



(Plate 12, figures 5 and 6) 



Three species of Homogalax have been described on Wasatchian 

 materials from the Bighorn Basin and all are about equal in size. In 

 all probability these represent but a single species, although Wortman 

 (1896) has attempted to distinguish between them on the basis of 

 premolar characteristics. The earliest named, Homogalax semihians 

 (Cope), was based on a specimen in which there is a small deuterocone 

 on P^ and said to have a diastema between P^ and P^. P^ is missing 

 but the alveoli are present to show that there was no diastema in this 

 position. However, the molars in the type are badly worn and because 

 the premolars seem relatively small there is no certainty that the 

 specimen actually represents Homogalax. A revision of the tapiroids 

 currently under way by Leonard Radinsl-cy at Yale University may 

 resolve this problem. The type of Homogalax was designated by 

 Hay as H. primaevus — one of two species named by Wortman in 1896 

 and characterized as lacking a deuterocone on P-. The other, H. pro- 

 tapirinus, was characterized as possessing a strong deuterocone on 

 this tooth. I suspect that this cusp, nearly f unctionless in a position so 

 far forward in the series, may well have been highly variable in 

 development. 



Seven specimens, consisting of maxillae, jaws, and separate teeth, 

 from the Bitter Creek locality represent Homogalax and are compara- 

 ble in size to the named Gray Bull species. None of the Bitter Creek 

 specimens exhibits P^ but U.S.N.M. No. 22^67 (pi. 12, fig. 5) has 

 comparatively well-developed deuterocones on P^ and P*, so that it 

 would be reasonable to suppose that this cusp was also present on P^ in 

 this individual. 



ISECTOLOPHID, near HOMOGALAX PRIMAEVUS (Wortman) 



Among the materials of Hyracotherium and Heptodon encountered 

 in the Knight exposures near Dad P. O. are remains of a small 

 perissodactyl that cannot be assigned to either of these genera. About 

 eight or nine specimens are included in the collections at hand and 

 nearly all are from the large promontory of exposures beneath the 

 Tipton tongue to the southwest of the State highway (330) bridge 

 over Muddy Creek. Included are jaws, maxillae, and isolated teeth 

 which represent a species about the size of the larger of the forms of 

 Hyracotherium from here. 



