132 



PROCEEDINGS OF THE ACADEMY OP 



Section of the Formations at Pyramid Mountain^ New Mexico. 



Subdivisions. 



5or6ft.| White, very compact silicious limestone. 



5 or 6 ft.| Hard, deep yellow gritty limestone. 



30 feet. 



25 feet. 



Bluish-gray clay of subschistose structure, 

 containing near the base a species of Gry- 

 pfuea and Ostrea, (referred by Mr. Marcou to 

 G. dilatata and 0. Marshii.*') 



Fine grained, white sandstone, disinte- 

 grating rapidly where exposed. 



80 feet. 



Hard, fine grained sandstone of a light 

 yellow color, forming perpendicular escarp- 

 ments. 



8 feet. I White, fine grained sandstone. 



200 ft. 



Alternations of red, green and white 

 marly clays. 



CO 



No. 3, 



lower 



No. 2. 





Mr. Marcou does not mention the occurrence of Inoceramus problematicus in 

 the limestone (a) of his section at this locility, but it has been found in this 

 position at various localities in the south-west by others, as stated in our last 

 communication. From the facts given by him, there is also scarcely room for 

 a doubt, but the specimen of Ostrea congesta, we mentioned seeing in his col- 

 leetionf (Proceed. Acad. Nat. Sci. November last) from Galisteo, was either 

 found in this bed or the clays immediately below it, {b of his section,) in both 

 of which deposits it occurs in Nebraska. 



As Pyramid Mountain is but an isolated portion, left by the denudation of 

 the surrounding strata, of a great elevated plateau known as the Llano Estacado, 

 which occupies a vast area of country in western Texas and New Mexico, it is 

 highly probable the beds composing Mr. Marcou's section are widely distributed 



• We think these identical with species found by Dr. George B. Shumard at Fort 

 Washita, Texas, where they appear to hold the same geological position, and are asso- 

 ciated with Ammonites vesperlimis (Morton.) Dr. B. F. Shumard has correctly, as we 

 believe, referred the first to (iryphcBa Pitcheri (Morton), and described the laiter as « 

 new specie*, under the name of Ostrea suhovate. (See Capt. Marcy's Report Explorations 

 Red River, page 205 — Appendix.) We are almost willing to hazard the opinion, that 

 these species will yet be found in Southern Nebraska, or north-eastern Kansas, in forma- 

 tion No. 2 of the Nebraska Section. 



t In alluding to this fact in our last paper, we inadvertently omitted to mention that the 

 specimen seen by us is in the possession of Prof Hall, by whose permission we referred 

 to its occurrence at that locaUty. 



[May, 



