428 Miscellaneous. 



At the same time the topographical character of the country entirely 

 changes. Instead of the low undulations of the prairies, hills of con- 

 siderable height with sharply defined outline, and but a short distance 

 beyond, real mountain ranges show themselves to the north, mark- 

 ing the limit between the rolling and mountainous region of Texas. 

 ' The place where I first met with a cretaceous deposit was at New 

 Braunfels, exactly where the old Precidio road from San Antonio to 

 Nacogdoches crosses the Guadaloupe. Here in the bed of the river 

 a white limestone is exposed which looks very similar to the " chalk 

 marl " of England, and to the " planerkalk " of Saxony. It is white, 

 rather compact, in some beds more marly, and occasionally it con- 

 tains green particles of silicate of iron. The stratification is per- 

 fectly horizontal. Some of the 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 diameter. Next to it comes a large species of Exogyra, 

 analogous in form to Exogyra costata, Say, but having concentric 

 laminae 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 Exogyra, there 

 are two species of Inoceramus, one of them being similar to the Ino- 

 ceramus Cuvieri, Sowerby, and the other to the Inoceramus Cripsiit 

 Mantell. The Pecten quadricostatus is also abundant in some beds, 

 a characteristic fossil, widely spread in cretaceous deposits. Of the 

 large family of the Brachiopoda, I saw but a few specimens of Te- 

 rebratula gracilis. The family of the Cephalopoda is not better repre- 

 sented. I saw two species of Ammonite, one of them of the section 

 which the Ammonites varians belongs to, and a Nautilus, which cer- 

 tainly is nearly allied to the common Nautilus simplex, if not iden- 

 tical 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 Guadaloupe, 

 and everywhere 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 so handsomely situated, consist 

 of limestone with the same mineralogical 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 Exogyra costata. Say, was met 

 with. It seems that this species among the fossils of the North 

 American cretaceous formation has the widest range. Besides its 

 most abundant occurrence in the cretaceous marl of New Jersey and 

 at some places in the Southern States, it is mentioned by Feather- 

 stonhaugh* to be frequent at different localities in the State of 

 Arkansas. 



From several facts I have obtained, it is certain that the same 

 limestone extends beyond Austin much farther to the north-east. On 

 the other side of the Guadaloupe, the limestone is exposed in many 



* Excursion into the Slave States, p. 119. 



