214 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



[P-] 



Feet. 



15. Gray, drab, and whitish limestone conglomerates, interstratified in the lower part, with 



bands of black and greenish shale from 40 to 100 feet thick; and associated with black 

 limestone holding layers of black chert from 1 to 3 inches thick. Graptolites occnr in 

 the black limestones and fragments of trilobitea in the chert. In the upper part the con- 

 glomerate is more massive, great thicknesses showing no trace of bedding. The inclosed 

 pebbles, bowlders, and fragments of limestone range in weight from 1 ounce to a ton and 

 in color from white through various shades of drab and gray to black. Associated with 

 the masses of limestone are occasionally others of gray calcareous sandstone, specimens 

 of which can not be distinguished from those of the sandstone (14) which^is beneath. 

 Some masses, which are of the same character as smaller inclosed blocks, are 200 feet long 

 by 30 feet thick. It is difficult to decide whether these are sediments deposited in the 

 bed or inclosed transported masses, notwithstanding that they are divided into beds 

 with partings of black shale. Some of the conglomerate beds are filled with pebbles of 

 black chert. Near to the top, patches of several hundred yards, in the supposed direc- 

 tion of the strike but without observed bedding, consist of light reddish-gray pure 

 limestone, in part highly crystalline, abounding with convoluted shells and other fossils. 

 The genera found in these conglomerates and their interstratified masses areGraptolithus, 

 Orthis, Rhynchonella, Camerella, Ophileta, Maclurea, Orthoceras, Asaphus, Illsenus, 

 Amphion, Bathyurus, Holometopus, Nileus, Ampyx, Agnostus, Endymion, and several 

 trilobites of undetermined genera. The determined species are Graptoliihus headi, Came- 

 rella calcifera, Maclurea ponderosa, Bathyurus saffordi, Holometopus angelini, Endymion 

 meehi, and Nileus scrutator 700 



[Q.] 



16. Greenish sandstones of a chloritic aspect, made up apparently of fine grains of quartz and 



feldspar, with a few scales of mica, mixed with greenish argillaceous matter. Some 

 beds are of a conglomerate character, the pebbles consisting of white quartz and red- 

 dish feldspar, varying from the sixteenth of an inch to an inch in diameter; the quartz 

 pebbles are somewhat larger and much more numerous than those of feldspar. They 

 are accompanied by occasional pebbles of red jasper, and by flat pieces of green shale. 

 In some beds the masses inclosed consist of gray limestone. The finer beds are aggre- 

 gated in thicknesses of several hundred feet, and the conglomerates are from 10 to 20 

 feet. These fine and coarse sandstones are interstratified with several bands of red shale 

 from 10 to 20 feet thick; and one of 60 feet consists of red shale interstratified with green 

 layers. The thickness of the whole was not measured, but it is supposed to be not much 

 under 2,000 



In his descriptions Logan included division N with divisions I, K, L, and M, in 

 a major group, but Billings *^*' classed N with O and P and commented on the 

 taxonomic relations as follows : 



The rocks of these divisions, in ascending order, consist of 277 feet of black bituminous 

 limestone, with some black shales, very fossihferous; next 700 feet of sandstones, in which no 

 fossils were collected or observed; and at the summit 700 feet of black shales, holding' gray 

 and white limestone conglomerates, abounding in fossils, although there are not a great many- 

 species. There appear to be in this series of strata two formations, distinguishable from each 

 other both by lithological and paleontological characters. The fiirst includes the black bitu- 

 minous limestones and shales, forming the upper 277 feet at Table Head, and those of Pistolet 

 Bay and 4 miles northeast from Portland Creek. The rocks at the latter locaHty appear to he 

 above the 700 feet of sandstone constituting division O and are therefore in the foregoing 

 descriptions of species referred to division P. Taking these three locahties to be on the same 

 or nearly the same horizon, we have from them, in addition to a few not yet described, the 

 following 48 species : 



Lingula nympha, 

 Lingula iole. 

 Lingula cyane. 

 Acrotr.eta gemma. 

 Orthis delicatula. 



* Strophomena aurora. 

 Strophomena imbecilis. 

 Strophomena decipiens (?). 

 Camerella parva. 

 Camerella varians. * 



