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‘A Sketch of the Geolovy of Texas. 361 
Strata abound in fossils. - The most common species is a small 
Ostrea, similar to Ostrea vesicularis, Lamk., but never growing 
as large and generally not being more than one inch in diame- 
ter. Next to it comes a large species of Exogyra, analogous: in 
fom to Exogyra costata, Say, but having concentric lamine 
instead of the oblique folds of that species. It certainly is the 
largest species of the genus, as some specimens of it are more 
than nine inches in length. Equally common with this Exo- 
gyra, there are two species of Inoceramus, one of them being 
similar to the Inoceramus Cuvieri, Sowerby, and the other to 
the Inoceramus cripsii, Mantell. The Pecten quadricostatus, 
is also abundant in some beds, a characteristic fossil, widely 
Spread in cretaceous deposits. Of the large family of the Bra- 
chiopoda, I saw but a few specimens of T'erebratula gracilis. The 
family of the Cephalopoda is not better represented. I saw two 
Species of Ammonite, one of them of the section which the Am- 
monites varians belongs to, and a Nautilus, which certainly is 
hearly allied to the common Nautilus simpler, if not identical 
With it. In one stratum which is only about five inches thick, 
sharks’ teeth of the genus Lamna and other genera abound. 
The same limestone ranges very far on both sides of the Gua- 
daloupe, and every where parallel to the chain of high hills or 
Mountains which separate the Indian country from the settled 
part of Texas. On one side I have followed it as far as Austin 
on the Colorado. The hills, on the slopes of which this city is 
80 handsomely situated, consist of limestone with the same mine- 
talogical and organic characters as that’ on the Guadaloupe. 
Among the fossils I found here a large Ammonite similar to the 
Ammonites Rhotomagensis, Sowerby. Near Austin also a single 
Specimen of the Eixogyra costata, Say, was met with. It seems 
that this species among the fossils of the North American creta- 
ceous formation has the widest range. Besides its most abun- 
dant occurrence in the cretaceous marl of New Jersey and at 
Some places in the Southern States, “it is mentioned wy me 
erstonhaugh* to be frequent at different localities in the State of 
_. From several facts I have obtained, it is certain that the same 
limestone extends beyond Austin much farther to the northeast. 
AP ea, - * Exenrsioncinto the Slave States, p. H9. 
Seconp Srnizs, Vol. I , No, 6.—Nov., 1846. vA 
