78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



The very well-defined cross crests and more forward-directed crista 

 obliqna of the lower molars, together with the elongate, uninterrupted 

 transverse lophs of the upper molars, show that these specimens should 

 not be included in Hyracotheruim. Moreover, a maxillary fragment, 

 U.S.N.M. No. 22788, with P^ and P*, shows P^ to be rather more like 

 Homogalax than Hyracotherium. It exhibits a very prominent para- 

 style and the talon is constricted lingual to this. The deuterocone is 

 very high and placed well forward with a high, more laterally directed 

 protoloph which does not join the ectoloph. There is no crest to the 

 tritocone. Kitts (1956) has noted the occasional absence of a crest 

 between the deuterocone and tritocone in P^ of Hyracotherium 

 craspedotum but I do not believe these teeth would otherwise be 

 confused. 



The tapiroid upper molars are readily distinguished from Heptodon 

 in the more buccally situated metacone, which is decidedly conical and 

 externally ribbed. Moreover, M3 has a particularly well-developed 

 and somewhat basined hypoconulid portion. The crests of the molars, 

 both uppers and lowers, are rather less elevated than in Heptodon. 



A rather close correspondence is seen to Graybullian material of 

 Homogalax primaevus but with specimens rather near the lower limit 

 in size. The molars, however, are relatively a little lower crowned than 

 in most of the Homogalax material examined. A close resemblance 

 is also evident in comparisons with the much larger materials of 

 Bridger Parisectolophus, but these later specimens show a relatively 

 longer trigonid portion in the lower molars, with a tendency toward 

 development of a basin approximating that of the talonid. 



Heretofore Homogalax has been considered as indicative of Gray- 

 bullian time but now there would appear to be little doubt but that 

 this genus, or a closely related isectolophid, is present in beds of 

 Lost Cabin age, in association with Heptodon and Lamhdotherium. 

 The encountering of such a form in these beds is, of course, not unex- 

 pected because of the continuity of this line into Bridgerian and 

 Uintan time. 



HELALETIDAE 

 HEPTODON VENTORUM (Cope) 



(Plate 13, figure 12) 



Nearly all of the La Barge tapiroid material can, on the basis of 

 size, be regarded as typical Heptodon ventorum, although as previ- 

 ously noted (1952) most of these specimens have teeth a little smaller 



