1902.] Matthew, A Honied Rodent from Colorado Miocene. 3^^ 



young individuals likewise appears small in proportion to the 

 first and second molars, but reaches its maximum of size 

 earlier than does the third molar. 



These observations are based on the American species, 

 which are a rather closely allied group, characteristic of the 

 Oligocene, and more primitive than the European assemblage 

 of species, which are characteristic of the Miocene epoch, and 

 in general larger, longer-toothed, and nearer to the modern 

 branches. The 5. viciacensis of the Upper Oligocene (St. 

 Gerand-le-Puy) appears to be the nearest to the American 

 group. The distinctions between our species have been based, 

 unfortunately, chiefly on the evanescent pattern of the teeth, 

 not sufficiently considering the great alteration due to a com- 

 paratively slight difference in their wear. Seven species 

 have been described, as follows: 



1. S. nebrascensis Leidy. White River, S. Dakota, skull and jaws. 



2. 5. pansus Cope. Loup Fork, N. Mexico, upper and lower jaws, etc. 



3. 5. peninsulatus Cope. John Day, Oregon, skull. 



4. S. gradatus Cope. John Day, Oregon, skull. 



5. 5. montanus Scott. White River, Montana, teeth and skeleton 



fragments. 



6. 5. hesperus Douglas. White River, Montana, lower jaw. 



7. S. complexus Douglas. White River, Montana, part of skull and 



jaws. 



I have at hand for comparison the types of all the species 

 except the first two, besides three other skulls and some less 

 complete material. I am indebted to the courtesy of Pro- 

 fessor Scott and Mr. Douglas for the loan of the type speci- 

 mens of the species described by ^ .^"Wx 



them. In revising these species (L^fe^TOf^M 

 it has been necessary to reject a r^l /I //I 1 f^j)\ 

 large part of the distinctions made t^^^*€^/L^/^)^==*^r^ J 

 by their authors, as being merely ] ^^ ^^7^7 ^""TT"^^ 

 a matter of different age in the pig. 5. stemojiher ^ubrascensis. 



, ■ Upper molars x ?. No. 1428. White 



type specimens. RiVer (Prowceras Beds), South Da- 



I. S. nebrascensis. I refer here ''""'■ 

 a skull. No. 1428, which, like Leidy's type, comes from the 

 Protoceras beds, and part of a lower jaw. No. 10286, in our 



