60 FOURTH UEPOKT — 1834. 



ville the hills are formed of the nummulite limestone, masses 

 of which are scattered in every direction: it is porous, and con- 

 tains spheroidal cavities, formed, no douht, by the decomposi- 

 tion of organic remains, which leave loose casts tliat are easily 

 washed out by the rains. The most characteristic fossil at this 

 place is Ostreci panda. 



" These limestone hills occur at intervals to the vicinity of 

 Jackson, on theTombeckbe : on Basset's Creek one of these hills 

 rises probably to a height of .300 feet above the water level. St. 

 Stephens is on a high bluff of this rock, wiiich, wherever it 

 occurs, forms a very broken or undulating surface. A short 

 distance above the village, the bluff rises nearly pei-pen- 

 dicular from the river, and is about 100 feet high. Every- 

 where in the vicinity this limestone crops out on the summits 

 of the hills, and myriads of Nummidites Mantelli are scattered 

 over the surface of the decomposing rock. The Gryphcca Vomer 

 is occasionally found among them, and the Ostrea panda, is 

 abundant; but no other fossils occur excepting what are pe- 

 culiar to the limestone in question. On the hills the Pecten 

 Poulsoni is in abundance. Near low-water mark in the bluff 

 is a stratum of shells, consisting of Ostrea panda and Plagio- 

 stoma diimosmn, both equally abundant. The surface of this 

 rock is in many places very hard and of a blueish colour, com- 

 pact and glittering when fractured, and is convertible into ex- 

 cellent lime. 



" Again it is often white and friable, and so much resembles 

 chalk that it is not surprising that it should have been mistaken 

 for the real chalk of commerce, from Avhich it differs, in pos- 

 sessing a coarse and more granulated structure, and in contain- 

 ing a considerable proportion of argillaceous earth." 



" Mississlpjn. — This State has an extensive marl tract in the 

 Chickasaw fields, near the borders of Tennessee." 



" Tennessee. — ^The south-western portion of Teimessee re- 

 presents a continuation of the tract just mentioned, which takes 

 a wcsterlj^ direction across the Mississippi River at the Chicka- 

 saw Bluff's." 



" L,ouiskma.— 'Qx . Pitcher, in a recent letter, describes an 

 extensive deposit of ferruginous sand between Alexandria and 

 Natchitoches. Judge Bry has also noticed it near the township 

 of Wachita, on the Wachita River, ^vhere it is recognised by 

 Belenniites^ Ammonites, and GryphtEa." 



" ylrhansas. — Mr. Nuttall long ago found fossils of this for- 

 mation on the calcareous platform of Red River, above and 

 below the junction of the Kiameska ; and Dr. Pitcher, of the 



