GASTEROPODA AND CEPHALOPODA OF THE RARITAN CLAYS 

 AND GREENSAND MARLS OF NEW JERSEY. 



By Robert P. Whitfield. 



PREIjIMINAEY eemarks. 



In offering the following descriptions and illustrations of the Gaste- 

 ropoda and Cephalopoda of the New Jersey marl beds to the public and to 

 scientific workers in similar fields, it is perhaps only just to add a word of 

 apology for the use of such meager material as is here presented, and that 

 apology must necessarily be that it is a,ll there is to present, being the best 

 material possessed. In studying these remains I have had the same diffi- 

 culties to encounter as those spoken of in the "preliminary remarks" to the 

 volume on the Brachiopoda and Lamellibranchiata;^ but in an extremely 

 exaggerated form, as the Grasteropods are represented in the several forma- 

 tions only by casts, much more exclusively than are the Brachiopods and 

 Laraellibranchs, and the Cephalopods largely by fragments. This, how- 

 ever, is not the only difficulty encountered, for these casts are far more 

 imperfect and consequently more difficult to understand. Among the 

 bivalves there is often the chance of obtaining the hinge structure and 

 muscular markings from impressions of single valves, and very commonly 

 imprints of the exterior show all the essential surface markings. This is 

 not the case, however, with casts of Gasteropods, for these usually repre- 

 sent only a small portion of the shell, as the apical portion of the spire is 

 almost invariably absent, that space not having been filled by sediment 

 before the shell was dissolved, and when present having often become solid 

 from deposits of shelly matter in these parts during the life of the animal. 



' Mon. U. S. Geol. Survey, Vol, 9, and Geol. Survey, N. J., Paleontology of the Cretaceous and 

 Tertiary, Vol. 1. 



13 



