14 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



A' Postnuclear whorls sculptured similarly throughout — Continued. 

 B' Varices absent — Continued. 



C Axial ribs present, rounded — Continued. 



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

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

 Intercostal spaces crossed by several spiral threads, base spirally 

 striated . 



Subgenus Besia Dall and Bartsch, 1904 (p. 135). 

 Type, Chrysallida convexa Carpenter. 



Spiral markings consisting of strong, raised threads or cords, equal to 

 or even stronger than axial ribs. 



Spiral cords equally spaced, and equally well developed between 

 the sutures and on the base; sculpture nodulose throughout. 

 Subgenus Mumiola A. Adams, 1864 (31). 



Type, Monoptygma spirata A. Adams. 



Spiral cords subequally spaced between the sutures, where the sculp- 

 ture is nodulose; base spirally lirate and axially striated. 

 Subgenus Chrysallida Carpenter, 1856 (p. 136). 

 Type, Chemnitzia communis C. B. Adams. 



Spiral cords confined to the base. 



Subgenus Egilina Dall and Bartsch, 1906. 



Type, Parthenia mariella A. Adams (45). 



Spiral markings consisting of impressed lines. 



Spiral striations subequally spaced, present between the sutures and 

 on the base of the whorls. 



Subgenus Pyrgulina A. Adams, 1864 (p. 169). 

 Type, Chrysallida casta A. Adams. 



Spiral striations on the base only, periphery deeply sulcated, axial 

 ribs extending to the umbilical region. 



Subgenus Egila Dall and Bartsch 1904 (p. 170). 

 Type, Parthenia lacunata Carpenter. 



Spiral striations on the base only, axial ribs terminating at the pe- 

 riphery, which is not sulcated. 



Subgenus Spiralinella Chaster, 1901 (32). 

 Type, Turbo spiralis Montagu. 



C ^ Axial ribs present, lamellar. 

 Spiral markings lamellar. 



Ribs and spiral lamellae moderately strong, subequally spaced be- 

 ■ tween the sutures and on the base; sculpture cuspidate. 

 Subgenus Haldra Dall and Bartsch, 1904 (p. 171). 

 Type, Chrysallida photis Carpenter. 



Ribs and spiral lamellae few, very strong. 



Subgenus Ividella, new name (p. 172). 



Type, Odostomia (Ividia) navisa, Dall and Bartsch. 



C ^ Axial ribs present but very feeble, usually only indicated near the sum- 

 mit of the whorls. 



Spiral markings consisting of several strong, broad, tumid cords, one or 

 more of the posterior cords crenulated. 



Subgenus Miralda A. Adams, 1864 (p. 176). 

 Type, Parthenia diadema A. Adams. 



