I2S Douglass — New Species of Merycochcerus in Montana. 



Art. XLI. — New Species of Merycochcerus in Montana. 

 Part I. By Earl Douglass. 



Description of the Skull of Merycochcerus laticeps n. sp. 



While making a collection of vertebrate fossils from the 

 Loup Fork beds of the Lower Madison Valley in Montana, 

 I obtained several parts of mandibles, representing three or 

 four different species, which were doubtfully referred to the 

 genus Merycochoerus. Three of the species were remarkable 

 for the depth of the rami. One, which was more slender 

 than the others, possessed characters which made it probable 

 that it belonged to the same genus ; though, measuring 

 beneath the middle lobes of the last molars, the deepest jaw 

 was double the depth of the narrower one. I could not iden- 

 tify any of these with species that had been described. 



In the summer of 1899 in some clay bluffs near the village 

 of New Chicago in Granite County, Montana, a nearly com- 

 plete skull and lower jaw with some other bone fragments 

 were found. The jaw was at once recognized as similar to one 

 of those found in the Madison bluffs. The greater part of the 

 skull was enclosed in a clay nodule. From some of the teeth 

 which were exposed it was supposed to be one of the Ore- 

 gon species of Merycochoerus ; but when cleaned from the 

 matrix it was seen to be very different, possessing many 

 peculiar characters which separate it from those forms. It is 

 more nearly related to the type represented by Merycochoerus 

 jproprius and M. 1'usticus, between which it is intermediate in 

 size. 



Its most striking characteristics are the following : 



Skull low, broad behind the orbits, narrowing rapidly toward 

 the front and back. Brain case short, the length behind the 

 post-frontal process being about one-half the distance in front 

 of it. Premaxillaries united in front forming a trough-shaped 

 depression, evidently for the accommodation of a proboscis. 

 Maxillaries deeply concave on the sides of the face — this, with 

 the malo-maxillary ridge which widens outward rapidly toward 

 the zygomatic arch, forming a broad nearly horizontal shelf 

 above the posterior premolars and anterior molars. Larger 

 part of external narial opening nearly between the orbits, but 

 continuing forward in a horizontal slit between the maxillaries. 

 Nasal bones short and ascending, placed far back, the anterior 

 tips being about midway between the inion and incisive border. 

 Foramen infraorbital placed farther back than in any other 

 species. Bending down of the face upon the basicranial 

 axis carried to the extreme, the shape of the posterior basal 



