128 



THE MERYCOIDODONTID/E 



Foramina: The infraorbital foramina lie above the anterior part of P\ The supraorbital 

 foramina are about 1 6 mm. apart. 



Dentition: Douglass said that the teeth are brachyhypsodont. Superior: The metastyle of 

 M 3 is moderately developed. Internal cingula on the molars are very faint or absent. There is a 

 tiny pit in the anteroexternal corner of P\ P 2 and P 3 have a well-developed anterointermediate 

 crest, and P 1 overlaps P 2 outwardly. The canines are large. Inferior: The metastylid of M 3 is very 

 large. The premolars are crowded, and the anterior three overlap. P 2 is unusually small, and Pi 



Fie. 83. — Promerycochcerus hollandi minor Douglass. Fragmentary skull and jaw. HT. 



size. (After Douglass, 1903.) 



Cat. No. 769 CM. 1/2 nat. 



is very large, laterally compressed, and lenticular in section. The posterior basin of P 4 is very large, 

 and that of P 3 is divided by the posterointermediate crest. The superior molar-premolar index is 

 0.87 and the inferior 0.83. 



Discussion: Douglass thought that this species seemed to be intermediate between E-poreodon 

 and Promerycochcerus. My belief is that it represents a dwarf variety in the Montana region, as 

 P. curvidens does in the John Day and P. vantasselensis pygma?us in the Great Plains area. I 

 should ally it with P. hollandi, in view of their many similar characters. 



Promerycochcerus leidyi (Bettany) 1876 

 Fig. 84 



Original Reference: On the genus Merycochosrus (family Oreodontidas). Quart. Jour. Geol. Soc. 

 London, XXXII, pp. 270-272, pi. XVIII (Merycochccrus leidyi). 



Type Localities: Probably near the head of Bridge Creek but possibly Great Canyon, nearly opposite 

 Old Camp Watson, John Day Valley, Oregon. Plesiotypes, Haystack Valley and Bridge Creek, in the same 

 area. 



Geologic Horizon: Lower Miocene (upper John Day). 



Types: Holotype, Cat. No. C.3299 W.M., skull and jaws united by matrix. Plesiotypes, Cat. Nos. 

 10956 and 10965 Y.P.M., skulls and jaws. The holotype was collected by Lord Walsingham, in the winter 

 of 1871-1872, and presented by him to the Woodwardian Museum, Cambridge, England. Named in honor 

 of Dr. Joseph Leidy. Cat. No. 10956 Y.P.M. was collected by William Day in 1876 and Cat. No. 10965 

 Y.P.M. by S. H. Snook in 1874. 



