126 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Tlie lower molars decrease in size from Mi to M3. The paraconids 

 are small and tend to assume a conical shape but are still connected to 

 the anterior protoconid crest. The paraconids are slightly internal 

 to the midline. Metaconids and protoconids are nearly equal. The 

 talonid is wider than the trigonid on Mi, about equal on M2, and 

 narrower on M3. On M1.3 the tliree talonid cusps are about equal in 

 height but the hypoconulid is smallest. On M3 the hypoconulid is 

 enlarged and projects posteriorly in the usual manner. 



The mandible is lighter than in Pentacodon and very closely ap- 

 proaches Palaeosinopa in all respects. 



P^ is 3-rooted and has a single outer cusp like that of P* on a smaller 

 scale save for the absence of a metacone. The protocone is small, and 

 there are no cingula. P^ is a pecuhar, large, heavy tooth. Its con- 

 tour is hourglass-shaped, with median constriction and expanded 

 equal inner and outer lobes. The paracone is nearly circular in sec- 

 tion and is heavy and tall and slopes slightly backward, like the pro- 

 toconid of P4. It is followed by a smaller metacone. There is only 

 the vaguest rudiment of a parastyle, but a very small metastyle is 

 present. The protocone is crescentic and large but lower than the 

 paracone. There is a small protoconule and rudimentary metaconule. 

 Approximately equal and expanded anterior and posterior cingula 

 occur on the protocone base, and each tends to develop into a cuspule 

 (protostyle and hypocone). The upper molars are of leptictid type, 

 strongly transverse, with emarginate external shelves, projecting 

 parastylar and metastylar lobes (especially on M^), metacones sHghtly 

 smaller than paracones, conules distinct, anterointernal cingula, and 

 low hypocones slightly more internal than the protocones. M^ is 

 reduced in the usual manner, with metastyle and hypocone absent and 

 metacone small. 



Table 27. — Numerical data on Aphronorus fraudator 



