PROMERYCOCHCERUS 119 



This species resembles Eporeodon in that the metastyle of M 3 is small and is not rotated so far 

 inward as is usual in Promerycochcerus ; the hypocone of M 3 is smaller than the protocone, whereas 

 in the other genus they are normally nearly equal in size; the skull size is close to that of the larger 

 eporeodonts; the anterior part of the zygoma is neither wide nor robust but has much the same 

 shape as that found in Eporeodon; from the matrix and field data it is very probably a middle John 

 Day form, which horizon has produced the greatest number and variety of species of Eporeodon but 

 only a few specimens of Promerycochoerus in the John Day Basin. 



I believe that this is a true member of the genus Promerycochoerus and that it may be con- 

 sidered a dwarf variety in the John Day region. However, since it occurs in the middle John Day, 

 it seems to me that it may be ancestral, perhaps directly to P. leidyi, with which it has certain char- 

 acters in common. 



Promerycochoerus erythroceps Stock 1932 

 PI. XV, figs. 1-3 



Original Reference: Additions to the mammalian fauna from the Tecuya Beds, California. Carnegie 

 Inst. Wash. Publ. No. 418, pp. 89-90, pi. 1, figs. 1, la, and lb. 



Type Locality: Tecuya Canyon, Kern County, California. C.I.T. Vert. Pal. Coll. Loc. 116. 



Geologic Horizon: Lower Miocene (Tecuya). 



Type: Holotype, Cat. No. 486 C.I.T., anterior part of muzzle, with I 3 , canines, right premolars, and part 

 of M l , and premaxillaries, together with anterior portion of nasal bones. The reddish color of the specimen sug- 

 gested the specific name. 



Specific Characters: In size Stock says that this species approaches P. superbus and also 

 resembles P. hesperus. There is so little of the skull that is diagnostic that comparisons with other 

 species are nearly impossible. The long nasals indicate that this form belongs in Promerycochoerus 

 and not in Merycochcerus. The maxillary convexity for the canine alveolus is very prominent. 

 Anterior to the maxillonasal notch, the nasals taper to their tips, a distance of 32 mm. They appear 

 to be broadest at the notch. 



Dentition: P 4 has a well-developed internal cingulum and no anteroexternal pit. In P 3 there 

 is no median crest but a well-marked anterointermediate crest. The anterior and posterior crescents 

 are joined and their basins confluent, thus differing in this character from the John Day and lower 

 Rosebud species of the genus, although in none of the species is the median crest more than weakly 

 developed, and there is a suggestion of the confluence of the anterior and posterior basins. This 

 California form is progressive in this respect. P 2 is like that in the John Day species. P 1 has 

 no posterior diastema. The general proportions and sizes of the premolars are intermediate between 

 those of P. carrikeri and P. chelydra, except that in the latter P 4 is longer than wide, and the reverse 

 is true in P. erythroceps. 



Promerycochcerus gregoryi Loomis 1924 

 Fig. 79; PI. XII; PI. XLVI, fig. 1 



Original Reference: Miocene oreodonts in the American Museum. Bull. Amer. Mus. Nat. Hist., LI, 

 Art. l,p. 23, fig. 12. 



Type Localities: Seven miles below Post Office on divide east of Porcupine Creek (HT), and five miles 

 south of Kyle Post Office (PT), both in South Dakota. 



Geologic Horizon: Lower Miocene (lower Rosebud). 



Types: Holotype, Cat. No. 12964 A.M.N.H., skull and anterior half of lower jaws, slightly crushed 

 laterally. According to Loomis, this skull is that of a female. Cat. No. 12962 A.M.N.H. is also a female. 

 Paratype, Cat. No. 13816 A.M.N.H., Loomis considers to be the skull of a male. Named in honor of Dr. 

 W. K. Gregory. 



