•/125. 120 j WATERS OF ROTTEN LIMESTONE — FOSSILS. 81 



Houlka, rejoins the main body on the Oka Tibby, below Palo Alto, on the May- 

 hew Prairie. South of the latter creek, the prairies, are distributed rather irregu- 

 larly over the surface of the cretaceous territory, yet on the whole retain their 

 character of dividing plateaux, between the Noxubee and Tombigbec, and the 

 several confluents of these streams. They are largiy interspersed with gently 

 undulating uplands, whose soil is generally greatly inferior in native fertility to 

 the prairie, and of a totally different character. It is on the outskirts, in 

 these wooded portions, and on the streams, not in the prairie proper, thai 

 the Rotten Limestone most frequently crops out, forming "bald prairie spots." 

 In all the lai-ger bodies of prairie, the rock is covered with a stratum of heavy, 

 pale yellow clay containing small round ferruginous concretions ; on whose 

 surface, by the addition of vegetable matter, the black prairie soil is formed, to 

 the depth of 12 to 18 inches. The thickness of this clay stratum varies greatly 

 — from 2 to 10, on the average about 5 to 7 feet. 



125. That under these circumstances, both spring-sand sipe-wells 

 cannot, as a general thing, exist in the prairies, may be readily- 

 imagined. The streams, while flooded during- the rainy season 

 and in fact, at every heavy rain, are dry during- the greater portion 

 of the year, unless indeed, like the Houlka, Tibby and Noxubee, 

 their supply derives from beyond the prairie region. Hence the 

 vast importance which the boring of deep, and partly artesian, 

 wells has acquired in this region. Where these have not been 

 obtained, cisterns are in general use, which are excavated into the 

 Rotten Limestone, without any cement being required to make 

 them hold water ; for the rock is sufficiently impervious for all 

 practical purposes. 



126. Fossils of the Rotten Limestone. — The larger streams, 

 as may be supposed, have mostly excavated their channels into the 

 Rotten Limestone, which appears at every turn, in localities too 

 numerous to be mentioned, not only on the immediate banks, but 

 frequently also on bluffs at some distance from the channels, whose 

 summits are on a level with the prairie. The Noxubee River at 

 Macon flows in a deep channel in the Rotten Limestone; the Houlka t 

 Chuckatonche, Tibby, Scooba, and others, exhibit the same phe- 

 nomena with frequency, and one outcrop is very nearly a copy of 

 every other. 



The shells most commonly found have been mentioned above (1T116), besides 

 which, Gryphaea vomer, Ostrea plumosa, 0. cretacea, Anomia argentea, Plicatula 

 nrticosa, a Lima (resembling Ctenoides acutilineata Con.) and two species of 

 Pecten, flat, and finely ruled ; together with shark's teeth, are among the more 

 common. 



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