LOWER CRETACEOUS SERIES. 717 



have broken abruptly across the strata. It is observed too of the dykes that 

 they enlarge downward. 



Trinity sand forms the body of the sharp crested hills one-half mile south- 

 west of Sierra Blanca Junction as a gray to yellow quartzite, through which 

 numerous interstratal dykes of porphyry have been injected. In the sand 

 proper no organic remains have been found, and with the exception of the 

 Actseonella horizon in Flat Mesa, no fossil remains were seen within the limits 

 of the sand. 



In the quartzite of the hill one-half mile southwest of Sierra Blanca there 

 is a band of fossiliferous limestone occupying about the same relative posi- 

 tion as the Actaeonella horizon in Flat Mesa, but the fossils are destroyed be- 

 yond recognition by metamorphism. 



Along the base of the Eagle Mountains, from the Carpenter Spring section 

 southward to Finney's Ranch, there extends a bed of sandstone, with an ex- 

 tensive development of limestone overlying in succession of strata, that shows 

 quite conclusively that the sand is that of the Trinity division. The section 

 at Finney's Ranch will show its relation to that of Flat Mesa: 



1. Massive limestone, with numerous intrusive dykes of porphyry between the 



strata 450 feet. 



2. Brown mottled quartzitic sand 25 feet. 



3. Calcareous brown sandstone containing small Exogyra resembling young of 



E. costata 40 feet. 



4. Caprotina limestone 10 feet. 



5. Arenaceous limestone 40 feet. 



6. Brown quartzitic sandstone « . . 40 feet. 



7. Limestone, with oysters and gasteropoda , 1 to 2 feet. 



8. Brown quartzitic sandstone 188 feet. 



The Caprotina fossil was found in great numbers, but the Caprina which 

 was found in the limestone below the Caprotina in Flat Mesa was not found 

 in the similarly related limestone at Finney's Ranch. The local metamorph- 

 ism of the stratified rock is very great in proximity to the porphyry pi 

 Eagle Mountain, and a great many of the fossil forms have doubtless been 

 destroyed. The shell of the Caprotina, however, is very refractory. I have 

 seen it clearly marked in granular marble, when almost every other form 

 would have been destroyed. 



FREDERICKSBURG DIVISION. 



The transition from the Trinity sands to the Caprina bed is through a hori- 

 zon of fifteen feet of flaggy calcareous sandstone and siliceous limestone, in 

 which are numerous gasteropods and Exogyra texana. This is the first and 

 lower Texana horizon, and corresponds to the Texana horizon at the base of 

 the Comanche Peak bed of the Colorado section. 



