658 W. T. LEE STRATIGRArHY OF COAL FIELDS OF NEW MEXICO 



more stratigrapliically higher in the section there is a zone about 50 feet 

 thick containing large concretions of limestone^ many of which are fos- 

 siliferous. These concretions contain Inoceramus fragilis H. and M., 

 Volutoderma sp., Prionotropis sp., and Pachydiscus n. sp. 



Some of the ammonites are very large. Pachydiscus, the largest one 

 found, probably measured between 2 and 3 feet across when complete, 

 but only a small part of it was obtained. About 100 feet stratigraphically 

 above the concretions just mentioned some thin layers of limestone in 

 the shale yielded Ostrea sp., Inoceramus fragilis H. and M., Inoceramus 

 sp. related to 1. dimidius White, Scaphites warreni M. and H., and Prio- 

 notropis sp. (United States Geological Survey locality number 3542). 



East of the last named locality the surface is nearly level and the shale 

 is more or less covered with soil. However, in a small ridge about 1,800 

 feet east of this locality and at a horizon somewhat higher a few poorly 

 preserved specimens of Inoceramus were found, which are either Inocera- 

 mus deformis Meek or a variety closely resembling it. The fossils sug- 

 gest correlation with the Xiobrara formation and also with the Punta de 

 la Mesa sandstone, but the lithology does not admit of either correlation. 

 About a mile farther east and at a still higher horizon the shale contains 

 numerous concretions of limestone which are very fossiliferous. This 

 probably represents the zone of concretions near the top of the Mancos 

 shale west of Eogers that yielded the fossils named in the Eogers section 

 (numbers 7164 and 7165). The following species were collected from 

 these concretions :' 



Fossils collected a'boiit 5 Miles 'Northwest of Cerrillos, Neiv Mexico 



(United States Geological Survey localities numbers 3532 and 7166) 



Ostrea sp. Liopistha undata M. «& H. 



Exogyra ponderosa Roemer Cor'bula sp. 



Inoceramus sagensis Owen Mactra ? sp. 



" irregularis Johnson C^jrodes sp. 



" sp. Anchura sp. 



Lcda sp. yautihis dekayi Morton 



Cucullwa ? sp. BacHlitcs asper Morton? 



Niicnla sp. Hamites sp. 



Cardium sp. Placenticcras planum Hyatt 

 Astarte sp. " sancarlosense Hyatt 



CrassatelUtes shumardi Meek Placenticcras sp. 



Cyprimeria sp. Stantonoceras pseudocostatus Johnson 



In commenting on the age relations of these fossils, Stanton states that 

 they are about the same as those from the top of the Mancos in the Rogers 

 section, of which he says: 



