PALEOCENE MAMMALS OF CENTRAL UTAH — GAZIN 



19 



The maxillary fragment, No. 15541, tentatively referred to Proto- 

 gonodon? spiekeri^ shows no important characters other than a rela- 

 tively great difference in size between M^ and M^ The isolated M'^ 

 is complete and shows a slight development of a mesostyle, not 

 nearly so prominent, however, as in Deuterogonodon montanus^ and 

 the slight hypocone is not nearly so lingual in position. 



In most respects, especially in the character of the trigonid of the 

 lower molars, P.? spiekeri stands in a relation nearly intermediate 

 between Protogonodon and Claen-odon, with perhaps a slightly greater 

 resemblance to Protogonodon. It is distinct from Deuterogonodon 

 montanus, as represented by the paratype, in the lowness of the cusps, 

 the far less developed crest and basin of the talonid, and in the 

 relatively greater importance of the entoconid. 



The anteroposterior diameters of the first and second lower molars 

 are 10 and 11 mm., respectively. The transverse diameters are 8 and 

 9.3 mm. 



PROTOGONODON BIATHELES. new species 



Type. — Portions of both rami of the mandible with Mi and Mg, 

 U.S.N.M. No. 16181. 



Horizon and locality. — Dragon Paleocene, Dragon Canyon, Emery 

 County, Utah. 



Specific characters. — Mi and M2 slightly larger than Protogono- 

 don? spiekeri. Paraconid median in position. Talonid relatively 

 wide. Teeth slightly rugose. 



Description. — Fragments of both rami of the mandible, No. 16181 

 (fig. 10), with Ml and M2, found in a mass of barite crystals to- 

 gether with well-worn upper teeth of Des- 

 niatoclaenus paracreodus in the Dragon hori- 

 zon, appear to represent a species of Proto- 

 gonodon distinct from P.? spiekeri. The 

 molars are only slightly larger than those in 

 P.? spiekeri.^ but in contrast with this form 

 the paraconid is much more median in posi- 

 tion, even in comparison with Protogonodon 

 pentacus. The trigonid portion is relatively 

 narrow, and the talonid, especially of M^, 

 is markedly wider and more basined than in 

 either P.? spiekeri or P. pentacus. This 

 specialization is directly opposite to that seen 

 in Protogonodon kimhetovius where the tal- 

 onid is relatively narrow. The enamel of 

 the teeth is very slightly rugose, much less so 

 in the talonid basin in comparison with P.? spiekeri, although the 

 teeth appear to be about as unworn as in the type of the latter. 



Figure 10. — Protogonodon 

 biatheUs, new species: Left 

 ramus of mandible with 

 M, and M2 (U.S.N.M. 

 No. 16181), type specimen, 

 lateral and occlusal views, 

 X ^Yz, Dragon Paleocene, 

 Utah. 



