THE C EN O ZOIC DEPOSITS OF TEXAS. 5 6 3 



of any other exposure referable to that horizon. Every con- 

 tact which I have observed also bears evidence to the fact. 



PLEISTOCENE. 



The Pleistocene deposits include the Equus beds and con- 

 nected deposits found along various rivers and creeks ; the 

 Coast clays and their'' extensions along rivers and creeks and 

 contemporaneous deposits of the Seymour plateau ; and the later 

 river, creek and surface deposits either of aqueous or subaerial 

 deposition. 



Equus beds. — In the valleys and depressions hollowed out by 

 the erosion of the Pliocene materials were laid down the ash- 

 colored limy sands and gravel which constitute the typical Equus 

 beds of San Diego and southwest Texas and the more ferrugin- 

 ous beds of the same age east of the Colorado. So far as I have 

 observed them they rest with great unconformity upon the Rey- 

 nosa, indeed, there is no equal unconformity visible between any 

 other two series of beds in the Texas Cenozoic. 



The deposits consist, in their typical exposures, of limy con- 

 glomeritic ashy material, containing pebbles derived from the 

 underlying Reynosa. The beds are without trace of stratification, 

 except that here and there through them the calcareous matter 

 appears as a line of nodules, or bed of pebbles will follow a 

 straight line for several feet. The beds are usually ashy yellow 

 in color, but lighter in places, and grade upward into a grayer 

 and more sandy body, and then into a black soil. Their ashy 

 appearance is one of their distinguishing characteristics. When 

 damp they are easily dug into, but when dry are very hard. 

 The vertebrate fossils, to which they owe their name, are found 

 in the lower portion of the beds, while they are rare in the upper 

 or grayer portion, which carries instead a number of forms of 

 land and fresh water shells. However, no line of division can 

 be drawn between the two portions as the change is very gradual. 



The thickness of the beds, so far as observed, is in no place 

 over 20 feet, and they appear to occur in detached and irregular 

 basins, usually connected directly with some drainage channel, 



