8io 



NORTH AMERICAN INDEX FOSSILS. 



broadly rounded in front, narrowly so posteriorly; surface smooth 

 except for lines of growth. 



Ripleyan of New Jersey, Alabama and Mississippi. 



Family Tornatinid^ Fischer. 

 CCIV. Volvula Adams. 

 Cylindrical with concealed spire ; long, narrow aperture, pointed 

 above, rounded below. Eocenic-Recent. 

 652. V. iota (Conrad). (Fig. 1 193, a, b.) Miocenic. 



Fig. 



193- 



a, Volvula iota marylandica ; b, V. iota diminuta ; c, Cylichna calvert- 

 ensis. (Md. Survey.) 



Minute ; a few impressed spirals near each end, aperture narrow- 

 est at center ; in var. marylandica Martin, apertural end is strongly 

 pointed above, shell narrowing towards each end ; variety diminuta 

 Martin is more cylindrical, the upper end less pointed, base of 

 aperture broad; var. calverta Martin has a proportionally greater 

 diameter than diminuta, and variety patuxentia Martin is wider 

 below than above. 



Chesapeakean of Atlantic coast. 



Family Scaphandrhle. 

 CCV. Cylichna Loven. 



Like the preceding, but spire deeply sunken leaving apical per- 

 foration ; columella with plications, often umbilicated. Triassic- 

 Recent. 

 653. C. costata Gabb. Cretacic. 



Rather large, with aperture widening towards base ; whorls more 

 nearly cylindrical than in the next species ; a single fold near the 

 base of the columellar lip ; surface with broad spirals. 



Nanaimo of Vancouver and northwestern United States. 



