NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 45 



deuterocone of P^, and the less deeply basined talonid of P4. Their 

 general form is, nevertheless, remarkably similar. 



The molar teeth of Shnimeryx are somewhat less progressive than 

 those of Hypertragulus in the achievement of selenodonty. The upper 

 molars lack the mesostyle as do those of Hypertragulus, but are a 

 little more brachydont, exhibit a slight external cingulum, and the 

 external rib of the metacone is less outstanding. The less-selenodont 

 character is most noticeable in the lingual portion of the upper teeth, 

 in which the stage of development approximates that in Protoreodon. 

 A small protoconule is preserved on the anteroexternal crest of the 

 protocone, and the posterior crest of the protocone is directed toward 

 the anterior wall of the metaconule, about as in Protoreodon. Also, 

 the anterior crest of the hypoconid of the lower molars is directed 

 toward the posterior crest of the protoconid so as to leave a small 

 pocket or basin anteroexternal to the entoconid, somewhat as in 

 Protoreodon, though perhaps less conspicuously. Selenodonty is 

 rather advanced beyond that of the homacodonts. However, as Stock 

 has pointed out, Simimeryx most nearly resembles Mesonieryx among 

 the various homacodonts. Although differences were noted, some were 

 only of degree, and there is strong indication that a homacodont 

 rather like Mesomeryx gave rise to Simimeryx. The leptotragulids 

 on the other hand, even as early as Uinta B time, were too highly 

 specialized to be considered as potential ancestors or to have been 

 derived from the same homacodont stock, 



SIMIMERYX HUDS0NI13 Stock, 1934 



Type.—Kxght maxilla with P- to M^ inclusive, C.I.T. No. 1764. 

 Horizon and locality. — Sespe upper Eocene, C.I.T. loc. 150, Pearson 

 Ranch, north side of Simi Valley, Ventura County, Calif. 



MEASUREMENTS IN MILLIMETERS OF DENTITIONS IN SPECIMENS OF 



Simimeryx hudsoni 



C.I.T. 



No. 

 1764 

 Type 



Length of upper cheek tooth series, P°-M', inclusive 28.9 



Upper premolar series, P^-P*, inclusive 13.4 



Upper molar series, M^-M^ inclusive 15.8 



P^ anteroposterior diameter : greatest transverse diameter 4.4 : 1.7 



P^ anteroposterior diameter 5.3 



P*, anteroposterior diameter : transverse diameter* 4.2 : 4.4 



M*, anteroposterior diameter : transverse diameter* 54: 5-9 



M^ anteroposterior diameter : transverse diameter 6.1 : 7.2 



M^, anteroposterior diameter : transverse diameter 5-5' 7-2 



1^ Illustrated in Stock, 1934, pi. i. 



