NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 3I 



"The limestones of the Wichita formation are for the most part highly fossil- 

 iferous, though in many of the beds good specimens are hard to obtain. A list 

 of the invertebrate fossils obtained from these beds has been published elsewhere. 

 (vSee table 2, page 106.) Collections of vertebrate remains have been made at various 

 times in Archer and Baylor Counties. A list of localities where the earlier collections 

 were made is given by Cummins. In many places the remains are found at the surface, 

 having weathered out of the clays or lime beds. Certain strata, called the 'bone-beds,' 

 have furnished most of the material. A chalky friable limestone exposed in a 

 railway cut just west of Mabelle Station, in Baylor County, is filled with fragments 

 of vertebrate remains allied to Eryops, mostly indeterminable. In a recent paper 

 Williston announces the discovery of a new genus and new species of amphibian 

 allied to Eryops, which he names Trcmatops millcri. This specimen is said to have 

 been found on Craddock's ranch, near Seymour. The figure of the skull given by 

 Williston shows a close correspondence to one found by the writer in the friable 

 limestone at the railway cut near Mabelle, which was unfortunately broken and 

 in part lost before opportunity was given for identification. It seems probable 

 that both came from nearly the same horizon." 



THE DOUBLE MOUNTAIN FORMATION. 



Cummins's original account'' of this formation is as foUovi^s: 



"The Double Mountain, or Upper Beds of the Permian, are composed of sand- 

 stones, sandy shales, limestones, red and bluish clays, and thick beds of gypsum. 

 The limestones are quite earthy, and are often very full of the casts of fossils, the 

 newer types largely predominating. The shales are often highly impregnated with 

 common salt, and none of them are free from gypsum. The sandstones are red, 

 gray, and spotted, and are generally very friable. The gypsum beds are numerous, 

 and often very thick, and the seams of fibrous gypsum traverse and transect the 

 clays and shales in every direction, ranging from paper-Hke seams to those 10 inches 

 in thickness, and often making a perfect network of seams. Toward the western 

 boundary of these beds, the strata are much distorted and folded. It looks as if 

 there had been a hea\y lateral pressure from the west, crumpling the strata into 

 short folds. In the gypsum, the folds are often only an inch or two across." 



"The beds'' are composed of sandstones, sandy shales, red and bluish clays, 

 and thick beds of g>'psum. The Hmestones are generally of an earthy variety, and 

 in places have many casts of fossils, the newer types being more largely represented 

 than the older. The gypsum beds are numerous and many of them very thick. 

 All the clays and shales are impregnated with gypsum, and many of them carry 

 a large percentage of common salt. 



"The sandstones are very friable, and are of various colors, red, white, and 

 spotted." 



The author has found it very difficult to draw^ any exact line between 

 the Clear Fork and the Double Mountain, but is in agreement vi^ith Cummins 

 that there is, west of the line described by him (Cvunmins), a decided change 

 in the character of the sediments. This change is, however, rather gradually 

 accomplished. As far west as Haskell there is a conglomerate very similar, 

 both in character, thickness, and coloration, to the layer described as the 



* Cummins, First Annual Report, Geological Survey Texas, 1889, p. 188. 

 •■ Cummins, Second Annual Report, Geological Survey Texas, 1890, p. 402. 



