"Vl 15] COLUMBUS BLUFF — FOSSILS. 75 



The greenish micaceous sands form the main body of the hills on which the 

 town of Columbus stands, and of those of this region generally ; the Orange 

 Sand strata proper being rarely more than 10 to 15 feet in thickness on the 

 ridges, and often entirely absent. Frequently, however, the oxidizing action of 

 the atmosphere has tansformed the upper strata of the greenish sands into 

 reddish or yellow, which, however, may generally be distinguished by their 

 sharpness, and the casts of fossils they contain, though sometimes very sparingly 

 and poorly preserved. Casts of Baculites are perhaps those most commonly 

 occurring, but the tubular anastomising concretions mentioned in the section at 

 Dr. Tindall's bluff ( *[ 1 1 1> , Sec. 9), are still more common, and are frequently met 

 with on the road from Columbus to Aberdeen. The bluff at Columbus", the 

 highest portions of which are between 150 and 160 feet above low water level, 

 consists entirely of these micaceous sands, more or less fossiliferous, of various 

 shades of color, and with some indurate ledges. Sand precisely similar forms 

 the bluff at Waverley ; an analysis of the same is given below (^110). 



115. Fossils of the Tombigbee Sand Group. — The list of fossils in Dr. 

 Spillman's collection, given below, will furnish abetter view of the fauna of this 

 group, than I could have derived from my own observations. So far as I am 

 able to judge from the limited amount of attention I have thus far been able to 

 bestow on the paleontology of the cretaceous formation, Dr. Spillman's collec- 

 tion represents correctly: the fauna of the peculiar and prevalent facies of the 

 green micaceous sands, from Lowndes county to Big Brown's Creek in Tisho- 

 mingo. The subordinate facies of the black sands, however, which we find in 

 N. Tishomingo, presents some differences of character, which may be observed 

 for instance, in the rare occurrence of Cephalopods, and of the prevalent 

 characteristic fossil of the cretaceous— Exogyra costata ; while on the other 

 hand, the bivalve genera Venilla, Cardiwm, IsocarJia ?, CrasMtetla !, Solen, 

 Gervillia /, and, others, which are wanting at Plymouth Bluff, are prevalent. 

 There seems to exist a close stratigraphical and lithological connection, however, 

 between these black micaceous clays and the unquestionable Tombigbee Sands ; 

 otherwise the former might be suspected as representing the fauna of the Eu- 

 taw Group. Perhaps an opportunity might occur in Alabama of comparing- 

 the fauna of the Eutaw beds, with that of the black sands of Tishomingo. As 

 it stands, the latter appears to offer more analogy to the fossils of the Pkipley 

 Group, than to those of the Eotten Limestone ; to which otherwise, the fauna 

 of the Tombigbee sands bear a close relation. 



As regards the occurrence of the Tombigbee Sand Group in Alabama, the 

 sections on the Alabama River given by Mr. Thornton (Second Pieport, Appen- 

 dix 2, A) seem to demonstrate its existence there, although these strata do not 

 appear to have been identified by Tuomey with those of Plymouth Bluff. 



[For the catalogue of Dr. Spillman's collection of fossils from the strata of 

 this group, which was not completed in time for insertion into the text, see 

 AppendLx No. I.J 



