LOWEE CKETACEOUS. 593 



Ransome describes the four formations in detail. Fossils were obtained 

 chiefly from the Mm-al Umestone and Stanton reported oh them as follows: 



The collection consists of a considerable number of small lots of fossils, with seldom more 

 than three or four species from one locality, and it includes a number of undescribed forms. 

 The known species that are recognized, however, are sufficient to prove that only the fauna of 

 the lower Cretaceous, or Comanche series, is represented in the collection. The identified 

 species all occur in Texas, indicating that the waters in which the Arizona deposits were laid 

 down were directly connected with the Comanche sea of Texas and Mexico, which probably 

 did not extend much farther west than the Bisbee area. 



In the Texan region three principal divisions are recognized in the Comanche series — 

 Trinity, Fredericksburg, and Washita. AH of the identified species in tliis collection occur in 

 the Glen Kose beds of the lowest or Trinity division and only one of them (Lunatia pedemalis) 

 is known to pass up into the lower members of the Fredericksburg diAdsion. 



A list of species referable to the Glen Rose limestone of Texas follows. 



Dumble ^^ cites Aguilera's description of the Cretaceous in Mexico and gives 

 accounts of the strata west of Casita, near Zubiate, Hermosillo, and particularly 

 near CabuUona, northeast of La Morita, He says: 



By far the best exposure observed is that near CabuUona, northeast of La Morita. Here 

 appears a great series of Cretaceous rocks, probably including strata belonging to both the 

 Lower and Middle divisions of the Mexican geologists, with other beds of wMch I find no descrip- 

 tion at all. 



A section made about 2 miles from the CabuUona ranch house gave the following: 



1. Interbedded sands and clays of varied colors. The materials are altered in places 

 by metamorphism, some being quartzitic, and some of the clays hardened and greasy. There 

 are some intercalated andesitic beds and dikes of porphyry. The top was not seen, 1,000 feet. 



2. Massive limestones; light-colored semimarbles at the top, followed by brown and gray 

 limestone. All the beds are very fossiliferous, but the fossils appear only as cherty protuber- 

 ances on weathered surfaces and in many cases are so broken as to be scarcely distinguishable. 

 Among the forms certainly recognized were a small Gryphsea and a Trigonia (like T. emoryi). 

 The middle beds carry flints in considerable quantities, and the Gryphsea occurs in the basal 

 portion in great numbers, 500 feet. 



3. A series of interbedded marls and marly limestones, with large numbers of a very heavy 

 oyster, Trigonia, Cardita, and other forms, 900 feet. 



4. Quartzites, sands and interbedded clays or marls; bottom not seen, 400 feet. 

 Except for their metamorphosed condition, the uppermost beds of this section resemble 



very closely the "coal series" of the section made at Eagle Pass, Texas, and, like those beds, 

 they are coal-bearing. They cover quite an extensive area in this region but are badly cut up 

 and disturbed by eruptive intrusions. These beds comprise alternations of sands and clays 

 with ferruginous concretions (some of which are of lai^e size) , considerable quantities of gypsum, 

 and some petrified wood. The sandstones vary from fine-grained to grit, and the clays from 

 those nearly pure to those with a large admixture of sand. The metamorphism directly or 

 indirectly due to the volcanic extravasations which accompanied and followed the deposition 

 of these beds has produced, in addition to its indurating effects, bright-purple and greenish 

 colors in some places, so that some of the beds closely simulate those of the tufl' itself. The 

 beds are somewhat faulted and broken. Our work did not extend far enough to the north to 

 reach the top of the beds, which are certainly more than 1,000 feet in thickness. The only 

 fossils found were specimens of a small square-beaked oyster, which occurred just below the 

 coal. 



There are two beds of coal, both highly altered. The lower is quite grapliitic, and the 

 upper, wliile retaining the structure of bituminous coal, is an anthracite in its composition. 

 48011°— 12 38 



