90 



and I tnist he will allow me tlie same liberty with regard to his theo- 

 retical section. 



The Caprina limestone is intimately united to the Comanche Peak 

 group, forming generally the highest elevation on the table-land of 

 Texas. Directly below, is what Dr. Shumard calls the Comanclie 

 Peak group. Comanche Peak is a celebrated landmark in Johnston 

 County, and as the author has given this name to a special group of 

 rocks, it would have been desirable to have a section of it, but Dr. 

 Shumard gives a section of Shovel Mountain, in Burnet County, fifty 

 miles distant. The Shovel Mountain section is divided into seven- 

 teen numbers, comprising three slopes, that is to say, three portions 

 of the mountain where the strata are concealed from view. The 

 Exogyra Texana is found near the summit, and the Gryplioea Pitclieri 

 near the base ; the whole thickness of the section is 355 feet. The 

 list of fossils is given without regard to the subdivisions of the strata, 

 and no one of these fossils indicates the upper portion of the Upper 

 Cretaceous, either in America or Europe. Some of them, such as 

 Gryphoia Pitclieri, Ammonites Peruvianus (acuto carinatus), Am. 

 Pedernalis, Nerinea acus, and Toxaster Texanus, are forms indicating 

 the Neocomian group of Europe, and I should not be surprised if 

 these forms were all found together at Shovel Mountain in the same 

 subdivision at the base of the section, and not near the summit. The 

 other fossils, Exogyra Texana (Jlabellata), PJwladomya Sancti-Sabce, 

 Lima Wacoensis, Arcopagia Texana, Triginonia crenulata, Avellana 

 Texana, Cerithium Bosquense, Holectypus planatus, indicate forms of 

 the upper green sand of England, and are found, I suppose, near the 

 summit of Shovel ISIountain. 



Dr. Shumard gives no reason, stratigraphical or paleontological, for 

 putting the Caprina limestone and the Comanche Peak group) at the 

 summit of the series of cretaceous rocks of Texas, except that he 

 says, the Caprina limestone always caps the highest elevations of the 

 table-lands of Texas. This greater elevation does not make it, as a 

 matter of course, a more recent formation, and the contrary is often 

 the case all over the world. Roemer, who considers the cretaceous 

 strata of Texas table-lands as an equivalent of the Upper Chalk of 

 Europe, admits that the strata of the plateaux are older than those of 

 the Texas plains, such as the Austin limestone. 



From the imperfect section of Shovel Mountain, and the list of 

 fossils given by Dr. Shumard of Comanche Peah group, I consider that 

 group as of the age of the Green sand, and to be placed below the 

 AiMin limestone, and the cretaceous rocks of New Jersey ; and more, 

 I think it is not rigorously limited, including in the middle and at the 

 base strata, which are probably e(|uivalents of what Dr. Shumard 

 calls Indurated blue marl, and the upper portion or even perhaps the 

 whole of his ]Vashita limestone. 



