654 W. T. LEE STRATIGRAPHY OF COAL FIELDS OF NEW MEXICO 



and Hagan fields, but neither the coal nor the conglomerate overlying it 

 was found. It is evident that both the coal-bearing shale and the con- 

 glomerate are local in occurrence and of very restricted distribution. 



The shale overlying the conglomerate is ordinary dark-colored clay 

 shale of marine origin. A few shells of the genus Inoceramus were found 

 near the base. A stratum of sandstone and a zone of concretions of im- 

 pure limestone occur midway of the shale and contain fossils, but none 

 were collected. The limestone concretions probably represent the Gas- 

 tropod zone of the Eio Puerco field. 



The Tres Hermanos sandstone, at this locality only 20 feet thick, over- 

 lies the shale containing the Gastropod zone. It is very resistant and 

 forms a hogback more prominent than that of the Dakota. It consists 

 of thin irregular layers of sandstone an inch or less in thickness, on the 

 faces of which are ripple-marks, worm tracks, and markings of many 

 kinds. The sandy layers are separated in some places by films of shale. 

 A few imperfect casts of gastropods were found in this sandstone and 

 impressions supposed to be Halymenites major- are abundant in some 

 places. The species named in the accompanying section (number 7168) 

 were found in blocks of sandstone at the base of a cliff of the Tres Her- 

 manos sandstone where the section was measured. The sandstone is 

 unlike any other rocks near it and has a peculiar appearance that makes 

 its recognition easy. 



At a horizon estimated to be 100 feet stratigraphically above the Tres 

 Hermanos sandstone there is a small ridge formed by a limestone about 

 3 feet thick which presumably represents the Greenhorn limestone. It 

 contains great numbers of Inoceramus Idbiatus Schloth. At a higher 

 horizon, estimated as 500 feet above the base of the Cretaceous, Inoce- 

 ramus Jahiatus Schloth. and Prionocyclus wyomingensis Meek were found 

 in a limestone having a strong odor of petroleum. These fossils are 

 among those collected by D. W. Johnson at the town of Cerrillos near the 

 smelter and determined by him as belonging to the Colorado fauna (83, 

 page 103). They are as follows: 



Fossils collected near the Smelter at Cerrillos, Neto Mexico 



Ostrca lugulyris Conrad Prionocyclus sp. iiov. 



Inoceramus laMatus Schlotheim Priouotropis woolgari Mantell 



" dimidius White Rostellites dalli var. icellsi Johnson 



" . fragilis H. & M. " am'bigua Stanton ? 



" strongi Johnson Acmea cerrillosensis Johnson 



Scaphites warreni M. & H. Scurria ? coniformis Johnson 



Prionocyclus macomM Meek Beryx sp. undet 



" wyomingensis Meek 



