384 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



Bittium quadrifilatum, page 655. Rissoa interfossa, page 656. 

 Bittium asperum, page 655. Cerithiopsis purpurea, page 660. 



Bittium armillatum, page 655. Cerithiopsis fortior, page 660. 



Bittium fastigiatum, page 655. 



Of these, Bittium ?, var. esuriens Carpenter has proved to be a syno- 

 nym of Bittium attenuatum Carpenter, and Cerithiopsis fortior Car- 

 penter is synonymous with Rissoa interfossa, while Bittium asperum 

 was later diagnosed by him as Bittium rugatum, and Bittium fasti- 

 giatum is now referred to the genus Diastoma. 



In 1865 we find no additional species added to the Bittium fauna, 

 but a more complete diagnosis for— 



Bittium ? var. esuriens Carpenter. Cerithiopsis purpurea Carpenter. 

 Bittium attenuatum Carpenter. Cerithiopsis fortior Carpenter. 



Bittium quadrifilatum Carpenter. Cerithiopsis munitum Carpenter. 

 Reference to these descriptions can be found under each species in 

 the present text. 



The following year we find the complete diagnosis of — 

 Rissoa interfossa Carpenter, Bittium armillatum Carpenter, 



and a full description of the species listed in 1864 as Bittium asperum 

 Carpenter, which he now names Bittium rugatum Carpenter. Here 

 also he refers Turbonilla aspera Gabb properly to the present genus. 



The genus Bittium breaks up into several convenient groups, on 

 the west coast of America, which may be considered subgenera. 

 These are characterized in the following key: 



KEY TO THE SUBGENERA OF BITTIUM, OCCURRING ON THE WEST COAST OF AMERICA. 



Nuclear whorls with two spiral lirations. 



Postnuclear whorls having varices. Bittium Leach s. s. 



Postnuclear whorls without varices Lirobittium, new subgenus. Type B. (L.) 

 catalinense Bartsch. 

 Nuclear whorls smooth. 



Spiral sculpture predominating over the axial. Stylidium Dall. 



Spiral sculpture not predominating over the axial. Semibittium Cossmann. 



Bittium s. s. is represented by two species only in the area under 

 discussion, namely B. panamense Bartsch and B. johnstonx Bartsch, 

 the first coming from Panama, the last from Lower California, while 

 of Stylidium but one species, B. (S.) eschrichtii Middendorff, and two 

 subspecies, B. (S.) e. icelum Bartsch and B. (S.) e. montereyense are 

 known. 



To Semibittium I refer the following thirteen forms : 



armillatum Carpenter. attenuatum latifilosum Bartsch. 



purpureum Carpenter. subplanatum Bartsch. 



vancouverense Dall and Bartsch. rugatum Carpenter. 



attenuatum Carpenter. quadrijilatum Carpenter. 



attenuatum boreale Bartsch. nicholsi Bartsch. 



attenuatum multijilosum Bartsch. nitens Carpenter. 



