WEST AMERICAN PYRAMIDELLID MOLLUSKS. 11 



KEY TO THE SUBGENERA OP TURBONILLA. 



Shells without basal keels. 

 B ' Varices absent. 



Spiral sculpture absent, or if present consisting of microscopic striations 

 only. 



Surface of the early post-nuclear whorls marked by feeble axial ribs, 

 later ones smooth. 



Subgenus Ptycheulimella Sacco, 1892 (p. 59). 

 Type, Tomatella pyramidata Deshayes. 



Surface marked by strong axial ribs which terminate at the periphery 

 of the whorls, intercostal spaces excavated between the sutures. 

 Nuclear whorls helicoid on planorboid. 



Subgenus Chemnitzia Orbigny, 1839 (p. 33). 

 Type, Melania campanellse Philippi. 



Nuclear whorl elongate pupoid. 



Subgenus Nisiturris Dall and Bartsch, 1906. 

 Type, Chemnitzia crystallina Dunker. 

 Surface marked by strong axial ribs and intercostal spaces which extend 

 over the periphery to the umbilical region. 



Subgenus Turbonilla Risso, 1826 (p. 29). 



Type, TurboniUal^yr'' ^^ ^"^ Bartsch^ 

 [plicala Kisso. 



Spiral sculpture present, always stronger than microscopic striations. 

 C ' Axial sculpture consisting of well developed ribs. 



Spiral markings consisting of many very fine spiral striations. 

 Aperture subquadrate. 



Shell with peripheral sulcus. 

 Pselliogyra, new subgenus. 



Type, Turbonilla monocycla A. Adams. 

 Shell without peripheral sulcus. 

 Subgenus Strioturbonilla Sacco, 1892 (p. 40). 

 Type, Strioturbonilla alpina Sacco. 



Aperture suboval. 



Subgenus Pyrgolampros Sacco, 1892 (p. 59). 



Type, Pyrgolampros mioperplicatulus Sacco. 



Spiral marking absent between the sutures, base strongly spirally 

 Urate. 



Subgenus Sulcoturbonilla Sacco, 1892 (14). 

 Type, Tomatella turricula Eichwald. 



Spiral markings consisting of strong striations. 

 Summits of the whorls strongly shouldered. 



Subgenus Pyrgisculus Monterosato, 1884 (p. 126). 

 Type, Melania scalaris Philippi. 



Summits of the whorls not strongly shouldered. 

 Subgenus Pyrgiscus Philippi, 1841 (p. 74). 

 Type, Melania rufa Philippi. 



Spiral markings consisting of one or two strong punctate cords in 

 the intercostal spaces between the sutures; whorls slightly shoul- 

 dered. 



Subgenus Pyrgolidium Monterosato, 1884 (15). 

 Type, Pyrgolidium, roseum Montagu. 



