WEST AMERICAN PYRAMIDELLID MOLLUSKS. 15 



Postnuclear whorls sculptured similarly throughout— Continued. 

 B' Varices absent— Continued. 



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

 mit of the whorls— Continued. 



Spiral markings consisting of many subequally spaced lirations. 

 Whorls tabulated at the summit. 



Subgenus Ivara Dall and Bartsch, 1903 (p. 179). 



Type, Odostomia (Ivara) turricula Dall and Bartsch. 



Whorls not tabulated. 



Subgenus Evalina Dall and Bartsch, 1904 (p. 180). 



Type, Odostomia{Evalina) americana Dall and Bartsch. 



C-* Axial ribs usually reduced to mere lirations, frequently only present 

 between the spiral ridges. 



Spiral markings consisting of moderately well-developed cords usually 

 equally spaced and present between the sutures and on the base; 

 axial ribs indicated by faint threads between the spiral sculpture. 

 Shell umbilicated. 



Subgenus lolaea A. Adams, 1867 (p. 181). 

 Type, lole scitula A. Adams. 



Shell not umbilicated. 



Subgenus Menestho Moller, 1842 (p. 184). 

 Type, Turbo alhulus Fabricius. 



C^ Axial ribs absent; axial sculpture represented by lines of growth only. 

 Spiral markings consisting of many, usually subequally and universally 

 distributed impressed lines. 

 Shell elongate-conic. 



Subgenus Evalea A. Adams, 1860 (p. 192). 

 Type, Evalea elegans A. Adams. 



Shell short, subglobose. 



Subgenus Oda Monterosato, 1901 (33). 



Type, Odostomia dolioli/ormis Jeffreys. 



C® Axial sculpture absent, shell polished. 



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

 and the other at the summit of the whorls. 



Subgenus Cyclodostomia Sacco, 1892 (34). 

 Type, Cyclodostomia mutinensis Sacco. 



Spiral markings consisting of a more or less conspicuous tumid ridge 

 on the summit of the whorls. 



Subgenus Doliella Monterosato, 1880 (35). 

 Type, Odostomia nitens Jeffreys. 



Spiral markings consisting of a strong peripheral keel. 



Subgenus Scalenostoma Deshayes, 1863 (p. 229). 

 Type, Scalenostoma carinata Deshayes. 



Spiral markings consisting of a peripheral sulcus. 

 Subgenus Jordaniella Chaster, 1898 (36). 

 Type, Turbo nivosa Montagu. 



Spiral sculpture absent or indicated only by extremely fine micro- 

 scopic lines of growth or stria?; surface polished. 



Summits of the whorls with a strongly tabulated shoulder. 

 Subgenus Spiroclimax Morch, 1874 (37). 

 Type, Spiroclimax scalaris Morch. 



