WEST AMERICAN PYRAMIDELLID MOLLUSKS. 13 



A^ Shells with l^asal keels — Continued. 



Axial sculpture consisting of strong ribs — Continued. 

 Spiral sculpture present — Continued. 



Spiral sculpture consisting of two tumid ridges, one at the 

 periphery the other at the summit of the whorls, and many 

 fine striations in the intercostal spaces. 

 Subgenus Baldra (24). 



Type, Turhonilla {Baldra) archeri Dall and Bartsch. 

 Axial sculpture consisting of lines of growth only. 

 Spiral sculpture consisting of faint lirations. 



Subgenus Discobasis Cossmann, 1888 (25). 

 Type, Aciculina demissa Deshayes. 



KEY TO THE SUBGENERA OF ODOSTOMIA. 



A' Postnuclear whorls sculptured similarly throughout. 

 B ' Varices absent. 



C ' Axial ribs present, rounded. 



Spiral markings, when present, consisting of mere microscopic striations. 

 Shell inflated. 



Summit of the whorls slightly shouldered. 



Subgenus Elodiamea De Folin, 1884 (26). 



Type, Odostomia {Elodiamea) gisna, new name = 

 Elodia elegans De Folin, not Odostomia {Evalea) 

 elegans A. Adams, 1860. 

 Shell not inflated. 



Summit of the whorls not shouldered. 



Subgenus Odostomiella Bucquoy, Dautzenberg and 



Dollfus, 1883 (27). 

 Type, Rissoa doliolum Philippi. 



Summit of the whorls tabulated. 



Subgenus Salassia De Folin, 1885 (p. 134). 



Type, Odostomia {Salassia) tropidita, new name = 

 Salassia carinata De Folin. 

 Spiral markings consisting of a strong, broad, raised cord at the summit 

 of the whorls, separated from the remaining part by a strongly impressed 

 spiral groove. 



Subgenus Vilia Dall and Bartsch 1904 (28). 



Type, Odostomia { Vilia) pilsbryi Dall and Bartsch. 

 Spiral markings consisting of two tumid ridges, one at the periphery and 

 one at the summit of the whorls; with many striations on the base. 

 Subgenus Folinella Dall and Bartsch, 1904 (28). 

 Type, Amoura anguliferens De Folin. 

 Spiral markings consisting of several to many raised threads in the inter- 

 costal spaces, always less strongly developed than the axial ribs. 

 Intercostal spaces crossed by equally spaced, raised spiral threads, 

 sculpture reticulated. 



Subgenus Trabecula Monterosato 1884. 



Type, Odostomia jejfreysiana Monterosato (29). 

 Intercostal spaces crossed by several raised spiral threads, base not 

 spirally marked. 



Subgenus Parthenina Bucquoy, Dautzenberg. 



and Dollfus, 1883 (30). 

 Type, Turbo interstinctus Montagu. 



