64 GULF TERTIARY OF TEXAS. 



separating these formations is very irregular, and often long arms of coast 

 clay run far inland, especially along the river channels, where during the 

 deposition of the clay there were lagoons and embayments suitable for the 

 formation of such ]^eds. Hilgard* speaks of this formation as consisting of 

 "a group of partly littoral and estuary, partly swamp lagoon and nuviatile 

 deposits, whose thickness and location is manifestly dependent upon the 

 topographical features of the continent then (during the Champlain period) 

 in progress of slow depression, as shown by the nature of the deposits and 

 the numerous superenclosed generations of large cypress stumps imbedded 

 in laminated clays exhibiting the yearly fall of leaves." 



Dr. Ferdinand Rcemerj- says in reference to these coast deposits: "At the 

 head of Galveston Bay, and even near the town of Houston, I found, at a 

 height of twelve to twenty feet above the general level of the bay, large 

 deposits of shells of Gnathodon, a bivalve mollusc which lives abundantly in 

 the brackish waters along the coast of the Mexican Gulf, and in the Bay of 

 Galveston particularly. Some few oyster shells of the common kind occur 

 in these deposits of half fossilized Gnathodon shells, but there are no shells 

 different from those now living in the bay. Everything tends to the suppo- 

 sition that the conditions of climate, etc., at the period when these deposits 

 along the coasts of Texas were formed did not differ materially from the 

 present, except that a change in the relative level of the land and sea has 

 taken place." 



COAST CLAY SOILS. 



The country underlaid by this group of strata is a flat prairie, reaching 

 from the Gulf shore to the outcrop of the Fayette Beds. The soil is a fertile 

 black clay, very similar to that of the prairies of Western Texas. The land 

 is now used for very little else than a great cattle range, but is doubtless des- 

 tined in the future to become one of the richest agricultural regions in the 

 Southwest, as it combines all the advantages of a most productive soil with 

 those of a moist and temperate climate. 



*"On the Geological History of the Gulf of Mexico," American Journal of Science and 

 Arts, Yol. II, December, 1871, p. 11. 



f " Contributions to the Geology of Texas," American Journal of Science and Arts, Second 

 Series, Yol. VI, 1848, p. 22. 



