137 Midway Stage 13 



Besides many more or less characteristic Midwa^^ forms, the 

 writer has collected from this horizon Endimatoceras ulrichi, 

 Yoldia eborea, Venericardia alticostata var. , CalyptropJiorus velahis 

 var. compressjcs , all of which descend to the very base of the 

 Midway, and hocardia mediavia, found (rarely) in several Mid- 

 way beds, and the peculiar type of Volutilithes so characteristic 

 of this stage, including V. limopsis, V. rugatus var. sajfoi'di. 



The failure to recognize the Matthews' Landing horizon as 

 belonging to the Midway is due to the lack of paleontological 

 facts. To show how great the want of such information has 

 been perhaps one example will suffice. In the Report of the 

 Alabama Survey for 1894, p. 247, we find under Endimatoceras 

 ulridu White, the statement, "Found only in the Nautilus 

 rock," meaning thereby bed 17 of the section in question. 

 Now that we have collected well-preserved, or at least specifi- 

 cally identifiable, specimens of this species through the whole 

 stage, a range of about 200 feet, including nearly 100 feet of 

 the so-called "Ripley Cretaceous" of that report, we realize 

 that the field has not been very thoroughly surveyed either 

 geologically or paleontologically, and hence we feel at liberty to 

 follow the facts brought out by our own research regardless of 

 statements published previously by others. 



Lithologically the Midway beds are subject to rapid changes. 

 We have seen a firm limestone grade out laterally within a few 

 yards into an incoherent sand. What is black clay on one river 

 is often represented by calcareous layers on another; but upon 

 the whole the lower beds of the stage are sandy, clayey and cal- 

 careous, while the upper are generally clayey. The Lignitic 

 above is characterized by lignitic sands. 



Geology of the Midway Stage in Different States. 



Texas. 



Rio Grande sedion. — The exact limits of the Midway stage 

 along the Rio Grande are not known. Its very existence may 

 be questioned, yet from the few unsatisfactory fossils we have 

 seen from there, and the publications of Messrs. Dumble* and 

 Penrose, t we are inclined to believe that it reaches the river at 

 a point about 3 miles below the Maverick-W^ebb county line. 



Before passing to the Colorado river section we should note 

 the pecuhar fauna, Midway in part at least, found by Dr. 

 White, 18 miles southeast of Eagle Pass. It consists of 



*Jr. of Geol., vol. ii, 1894, P- 555- 



t ist Ann'l Rep't Geol. Surv. Texas, 1890, p. 13. 



