242 



DOUGLASS — FOSSIL MAMMALIA 



the second south of west of Whitehall, in Jefferson county. The strata containing the 

 bones are a sandy clay that swells and cracks on weathering and crackles under the feet 

 when dry, and a light-gray fine-grained homogeneous material. Under the microscope 

 the latter shows many angular, glassy fragments, which are undoubtedly volcanic dust. 

 The fossils have not all been determined. Most of them are new. The following is a 

 partial list : 



Ictops acutidens, sp. nov. 

 Eumys minor, sp. nov. 

 Oylindrodon fontis, gen. et sp. nov. 

 Sciurus jeffersoni, sp. nov. 

 Ischyromis typus Leidy. 

 Palmolagus temnodon, sp. nov. 

 Palceolagus triplex (?) Cope. 



Palmolagus turgidus (?) Cope. 



Hycenodon minutus, sp. nov. 



Agriochoerus maximus, sp. nov. 



Mesohippm bairdi (?). 



Leptoehcerus. 



Leptomeryx,. 



Hyracodon. 



Thompson Creek Beds. 



These are well exposed on a creek draining ;i small region northwest of Three Forks. 

 The stream is small and nearly dry in summer, and I do not know that it is named on 

 any map, but I have called it Thompson creek from the only man who lives near it. 

 If they were called Three Forks beds they would be confused with the Three Forks for- 

 mation which is Devonian. In these beds are the cracking clays above mentioned as 

 occurring on Pipestone creek, also light colored material resembling that occurring at 

 that place but containing lime. There are layers of limestone and strata of hard sand- 

 stone. 



Most of the fossils were found on the north branch of Thompson creek near the; 

 road to Boulder. Farther to the southwest an; large quantities of fossil wood, but- 

 only occasional bone fragments. The most abundant vertebrate remains are bones of 

 Titanotheres. These have not been studied, but they do not belong to the largest species. 



List of Fossils. 



Limnenetesplatyec.ps, gen. el, sp. nov. Mesohippm. 



I/imnenetes (?) anceps, sp. nov. Colodon. 



Agriochoerus minimus, sp. nov, r li I another hun. 



Toston Beds. 



These are exposed northeast of Toston, which is a small railroad station on the Mis- 

 souri river below Three Forks and above Townsend. They are about twenty.-five miles 

 north and east of the Thompson Creek beds. While the last named deposits apparently 

 belong to the lower White River or Titanotherium horizon, part, at least, of these seem to 



