RESUME OF LITEEATUEE. 129 



from their ordinary paleontologic associations. While the Lower Carboniferous 

 consists of sandstones, shales, and limestones, the Upper is confined almost 

 exclusively to massive beds of red sandstone. "In its lower strata the former 

 shows mainlj" j-ellowish sandstones, interstratified with yellowish and gray shales, 

 while higher up the blue limestone sets in, containing charactei'istic fossils. Imme- 

 diately above that the red sandstones begin, and continue in an unbroken series 

 until the white sandstones of the Lower Cretaceous are reached. Trias and Jura 

 are missing or reduced to a minimuui, and onh' exposed locally." 



The ''Lower Carboniferous" is reported by Endlich as entirely conformable with 

 the Devonian. There is, indeed, an apparent conformit}', but its earliest sediments 

 were deposited upon the Oura}' limestone only after the latter had undergone a 

 protracted period of erosion. Endlich gives no total or average thickness for this 

 formation, but he states the thickness of exposures at several points. Near station 

 49, apijarently, 1,000 feet were observed (p. 316); at station iO but 100 feet (p. 216); 

 and in the Animas Valley it would appear to have a thickness of 1,100 to 1,800 feet, 

 more or less (p. 219). Endlich found this sei'ies, which Cross has distinguished as 

 the Hermosa formation, to be sparing!}' fossiliferous, but from it Cross and his 

 associates have obtained extensive collections. Endlich cites Productus gemtstriatus, 

 Seminula subtillta^ and Spirlfer sp. The species first mentioned was not found in 

 the recent collections, and if its occurrence is authentic, as I doubt, it is of some 

 interest, seeing that the species is a rare one. Apparently, however, the name is a 

 blunder of Endlich's for the common Productus seiiiiretlculatus, for we seem to have 

 his fossils among our present collections, and they belong to the type wliich I have 

 discriminated as P. semireticulatiis rar. Jiermosanus. 



The red sandstone or Upper Carboniferous of Endlich succeeds the beds which 

 he calls Lower Carboniferous. This series consists principally of red sandstone, as 

 alreadj^ pointed out, but it seems to contain a certain amount of dai'k shale and to be 

 sometimes strikinglj' interstratified with beds of white sandstone (p. 218). At one 

 point a thin limestone occurs above the sandstone (p. 217). The thicknesses seen at 

 several points are 2,000 feet on the east side of the Animas, 1,400 feet at station 40, 

 and 1,800 feet on Bear Creek (p. 217). Fossils are reported as especiall}' scanty, but 

 Seminula suhtilita is cited, and also Productus si;)iilstrlatu.s, though the latter was 

 not found in place, and some doubt seems to have been entertained as to the 

 specimens really belonging to this hox'izon. Here also, if I judge correctly from 

 the context, are reported crinoids and corals similar to those found in the red sand- 

 stone of the Sangre de Ci'isto Range. Indeed, that formation to which Endlich gave 

 the name Arkansas sandstone he is disposed to regard as the stratigraphic equivalent 

 of the Upper Carboniferous of the San Juan region (p. 240). 



From the color of Endlich's Upper Carboniferous series, and the fact that it is 

 14364— No. 16—03 9 



