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



Ties Hermanos sandstone. The following species were collected at this 

 locality : 



Fossil Shells collected East of the Rio Puerco, ahout 3 Miles Noi'th of San 



Francisco, New Mexico 



(United States Geological Survey locality number 7204) 



Ostrea sp. Turritella sp. 



Pinna petrina White Pr-ionotropis sp. 



Cardiuin sp. Metoicoceras sp. 



Lunatia sp. Coilopoceras coUeti Hyatt 



The second collection is from an exposure about half a mile east of the 

 first and estimated to be stratigraphically higher by abont 100 feet. The 

 strata here dip very slightly to the east and the rocks are covered with 

 soil in most places. The shells collected at the higher horizon are as 

 follows : 



Shells collected East of the Rio Puerco, ahoiit 3 Miles North of San Francisco, 



Netv Mexico 



(United States Geological Survey locality number 7193) 



Ostrea luguhris Conrad Baculites gracilis Shumard? 



Anomia sp, Prionocyclus icyomingensis Meek 



Inoceramns fragilis H. & M. Scaphites tcarreni M. & H. 



Ancliura sp. Ptycliodus sp. (fish teeth) 

 Anisomyon ? sp. 



These fossils seem to indicate horizons several hundred feet above the 

 base of the Mancos, namely, near the Caphalopod zone, whereas their 

 apparent position as observed in the field is near the base of the Mancos 

 about 500 feet below the Caphalopod zone. It is possible that the rocks 

 have been faulted, so that the position of this zone in the section is de- 

 ceptive, bnt no indication of faults with displacement of more than 25 

 feet was noted near these localities. 



More detailed investigation of the Mancos from Eio Puerco westward 

 is necessary before its subdivisions and their relations to each other and 

 to neighboring formations are properly understood. The rocks dip at 

 low angles and broad grassy valleys occur at the outcrops of the shale. 

 The rocks are faulted and warped in some parts of this field, and it is 

 difficult to find a place where there is no liability of error in measuring 

 the shale in these broad valleys. Furthermore, the fauna is not so well 

 known that the vertical range of all the species can be confidently given. 

 A section measured by Darton (114, page 60) near Laguna, at the 

 southwestern extremity of the area shown on the accompanjing map, is 



