160 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



appears, however, to be no diastema, and the antemolar region of the 

 jaw is relatively shorter than in the other genera here considered, what- 

 ever may have been the exact number and homologies of the teeth. 



P4 is relatively higher, slenderer, and simpler than in Palaechthon. 

 In the two available specimens there is no clear trace of a metaconid, 

 and the paraconid is represented only by a very rudimentary and 

 scarcely visible angulation of the anterior edge. The heel is short but 

 is relatively broad and has a rudimentary basin and two very small 

 and poorly differentiated posterior cuspules. 



Mi_2 are almost identical in structure with those 

 of Palaechthon. The trigonid of M3 is also closely 

 similar, but the talonid is different. It is reduced, 

 more pointed posteriorly, with the third lobe de- 

 cidedly narrower and less clearly differentiated, and 

 the h3q30conulid apparently single. 



In the upper dentition, only M^~^ are now known. 

 These are basically similar to those of Palaechthon 

 but give quite a different superficial impression by 

 reason of their more delicate structure, more transverse and triangular 

 outhne, and the accentuated forward twist of the protocone, present 

 in the other primate genera but here most strongly developed. Para- 

 style and metastyle are distinct and subequal, as are protoconuie 

 and metaconule. The inner face of the protocone is flattened and 

 bears a faint vertical depression, but the base is not at all bilobed. The 

 posterointernal basin or expansion is only faintly indicated, less de- 

 veloped than in the other genera. M^ is short, rather strongly tri- 

 angular, and developed analogously to that of Palaechthon. 



Figure ZZ.—Paienochtha 

 7wino)-(Gidley),U.S,N.M, 

 no. 9590, left upper mo- 

 lars, crown view. Four 

 times natural size. (After 

 Gidley, 1923, fig. 4.) 



Table 35. — Individual measurements of Palenochtha minor 

 Type and Principal Referred Lower Jaws 



Upper Jaws (all known) 



