A SPIRAL BIVALVE SHELL FROM THE WAVERLY 

 GROUP OF PENNSYLVANIA. 



By Charles E. Beecher. 



The eastern development of the "Waverly group, has not been as 

 extensively examined by palaeontologists, as its importance would seem 

 to warrant, from its being the lowest member of the Carboniferous 

 series. This has arisen principally from the fact, that the rocks of the 

 group become much attenuated east of the State of Ohio, and are also 

 covered and obscured by the mass of overlying strata of tho lower coal 

 measures. Their close lithological resemblance to the underlying and 

 greatly developed Chemung series, has, in addition, rendered the group 

 comparatively inconspicuous. 



The fauna of this attenuated Waverly series in north-western Penn- 

 sylvania is, however, not commensurable with the thickness of the 

 strata. In the section of the rocks at Warren, and the list of Waverly 

 fossils at that locality, published in Proc. Am. Ass. Ad. Sci., vol. 33, 

 pp. 2-4, this disparagement is very evident. And it will be noticed 

 that the number of species is as large as from any locality where the 

 Waverly group forms a conspicuous physical feature ot the country. 



The Waverly deposits in Warren county, Pennsylvania, show many 

 evidences of having been formed not far from the shore-line. This 

 condition is indicated by the numerous mud furrows, land plants and 

 the drifted and worn shells. The interpolation of an extensive bed of 

 conglomerate, further shows that the sea-bottom was not in a condition 

 of repose. After the deposition of the conglomerate and the return of 

 the previous physical conditions, nearly the same fauna returned and 

 persisted to the base of the great Carboniferous conglomerate. A 

 region subject to these profound changes in the nature of the sedi- 

 ments, and to various oscillations of the sea-bottom, would be expected 

 to furnish many interesting faunal forms. The same varying con- 

 ditions are also present in the Chemung group of this region; and 

 these two series of strata, the Chemung and Waverly groups, present 

 the paleontologist with many species not yet observed elsewhere, and 

 also with several truly remarkable forms of life, among which may be 

 mentioned the Spiraxis Randalli of Newberry. But few of these have 

 [Assem. Doc. No. 104.] 21 



