. Annual report of the United States Geological Survey to the Secretary of the Interior . Cylindrite* formosus Cragin. Eriallaster texanus. Exogyra texana. Gryphrea marcoui. Diplopodia texanum. Cyprimeria crassa, in the lower part. Schli lenbachia acutoearinata. Sclili priil iacliia elegana shumardi tarrantonsis plexa Cragin. 1 Trans. Acad. Sci. St. Louis, Vol. I, U. S. GEOLOGICAL SURVEY TWENTY -FIRST ANNUAL REPORT PART VII PL. XXVII. 1. la, 1&. Exogyra texana Roemer. 2a. 2b. Gryphaea ma
. Annual report of the United States Geological Survey to the Secretary of the Interior . Cylindrite* formosus Cragin. Eriallaster texanus. Exogyra texana. Gryphrea marcoui. Diplopodia texanum. Cyprimeria crassa, in the lower part. Schli lenbachia acutoearinata. Sclili priil iacliia elegana shumardi tarrantonsis plexa Cragin. 1 Trans. Acad. Sci. St. Louis, Vol. I, U. S. GEOLOGICAL SURVEY TWENTY -FIRST ANNUAL REPORT PART VII PL. XXVII. 1. la, 1&. Exogyra texana Roemer. 2a. 2b. Gryphaea marcoui Hill and Vaughan. 3a, 3b. Pseudodiadema texanum , 46. Enallaster texanus Roemer. INOIS HILL.] EDWARDS LIMESTONE. 227 :v<iym texana and EeJtiriodcrututu are especially abundant in thebasal portion of the formation, which is marked by the absence of theRudistes and Requienia species characterizing the overlying Edwardslimestone. EDWARDS AND COMPOSITION. The Comanche Peak formation passes up without break into theharder and more persistent Edwards limestone. In general the twoformations can be distinguished by the fact that while the ComanchePeak strata are less consolidated, are slightly argillaceous, and possessa more marly texture, the Edwards limestone is largely a firm, white,ringing limestone of great hardness and durability. The Edwards alsoweathers into cliffs, while the Comanche Peak is wrought into lower-lying slopes. Finally, the Edwards limestone is distinguished fromthe Comanche
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