INSTITUTE OF SCIENCE, PHILADELPHIA. 323 



manuscript report on the Gastropods of the New Jersey marls, under the 

 specific name of Dallii by Prof R. P. Whitfield. 



Family SOLARIID^. 

 Genus SOLARIUM Lamarck. 



This group occurs in remarkable abundance in our Eocene, but has been 

 generally misunderstood, the small Trochoid pearly shells properly called 

 Solariella having here, as in Europe, been frequently described under the 

 name of Solarium, which latter is never pearly, and belongs to a wholly di- 

 verse line of development. 



The examination of our fossil species has led me to believe that a sub- 

 division of them into sections would aid students in identifying the species, 

 and it has therefore been attempted. It should be premised that the form of 

 the shell in most of the groups mayvary by having : (i) the whorls rounded at 

 the periphery ; or (2) the periphery keeled ; or (3) with a shallow, wide sulcus 

 on the top or base of the whorl near the periphery ; or (4) by having the spiral 

 sculpture simple or granular along the threads. These variations may occur 

 within what we have been accustomed to regard as specific limits among the 

 Eocene species, though perhaps in the existing fauna the limits of variation 

 in these particulars are less inclusive. 



Eliminating all the Trochacea and Adeorbidce from among the species to 

 be considered, we find the remainder fall naturally into four sections, which 

 represent the groups respectively typified by 5. elaboraUtin Conrad, 6'. scro- 

 biculatiini Conrad, S. alveatum Conrad, and 6". graiudatiim Lamarck, and 

 characterized as follows : 



1. Section Solariaxis ; shell with the umbilicus scalar, the umbilical wall 

 with a rib between the umbilical carina (or basal margin of the umbilicus) and 

 the suture above; the umbilical carina annulate; sculpture, except lines of 

 growth, exclusively spiral, the spirals linear or granular; periphery rounded 

 or sharp, with a feeble margination or none. Type 6'. elaboratnm Conrad. 



2. Section Patu/axzs ; shell with the umbilicus funicular ; umbilical rib 

 absent; umbilical carina tubercular ; sculpture radial and spiral, usually feeble 

 or obsolete; periphery sharp, thin, usually decumbent, not marginate. Type 

 S. scrobicidatuin Conrad. 



3. Se-ztS-Qn Stellaxis ; shell with the umbilicus scalar ; umbilical rib thread- 

 like ; umbilical carina coarsely toothed ; sculpture strong, not granular, sparse 

 especially above ; periphery carinate and strongly marginate. Type 5. alve- 

 atum Conrad. 



4. Section Solarium s. s. Umbilicus scalar, with no umbilical rib ; umbili- 

 cal carina annulate or tuberculate, set off from the base by a deep, narrow sul- 

 cus ; surface sculptured in both senses, the radial sculpture well marked ; 

 periphery usually keeled, marginate or with prominent peripheral spiral ribs. 

 Type S. perspectivum Lam., S. gramdatum Lam., etc. 



