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x\RT. XX. — Observations on a group of Cretaceous Fossil Shells, found in Tippah 

 County, Miss., with descriptions of fifty-six new species. 



By T. A. Conrad. 



The Cretaceous strata of Mississippi have long since been observed and partially 

 noticed by geologists, and the lamented Professor Tuomey has described a number of 

 their fossil contents. I now introduce quite a distinct group of shells, which are 

 imbedded in a different matrix compared with the prevalent cretaceous marls, green 

 sand and limestones. The discovery of these beautiful organic remains is due to the 

 indefatigable exertions of Dr. W. Spillman, of Columbus, who has forwarded a 

 collection of specimens more or less perfect, consisting of nearly sixty species, all of 

 which appear to be unpublished except Scaphites Conradi. The appearance of these 

 shells is like that of eocene species which have merely lost their animal matter, and 

 in this respect are very unlike the condition of similar genera in the contiguous rocks 

 of the same era. The fossils are imbedded in a sandy marl of a dark gray color, the 

 principal constituents of which are fine scales of mica and grains of quartz mixed with 

 fragments of small shells ; and though some of the very thin species are distorted, the 

 stronger retain their original shapes and are generally very perfect. Species of 

 Crassatella, Nucula and Meretrlx have the valves united as in life, as well as a 

 few of the extremely thin Inocerami, though the latter have been more or less distorted 

 by pressure. The numerical proportion of species of Cephala and Acephala is nearly 

 equal. The external sculpture of all is as sharply defined as in existing species. 

 Besides Scaphites and Baculites, there is only one shell in the collection which 

 resembles a species of the green sand or limestone, and it is quite distinct. The rare genus 

 Pulvinites is herein for the first time introduced as an American form. The analogous 

 species, as well as that of Gervillia, occurs in the Baculite limestone of France and 

 Normandy, which I believe is referred by D'Orbigny to his Senonien Stage, the same 

 in which he includes the Cretaceous fossils of North America. 



It is interesting to find bivalves of so remote an era in sufficient preservation to 

 exhibit generic characters as clearly defined as they are in living shells. In this 

 condition are the hinges of Gervillia, Pulvinites, Ctenoides and Cardium. There 

 are also specimens of Baculites and Scaphites which exhibit the interior divested of 

 all extraneous matter, and delight the eye with exquisite curves of the foliated septa, 

 whilst the shells glow with brilliant iridescent tints. 



