no. 1823. MOLLUSKS OF THE GENUS CERITHIOPSIS— BARTSCH. 329 



than are present on the early post-nuclear turns. To this group I 

 would apply the subgeneric name CeritMopsida. The two species are 

 Cerithiopsis (CeritMopsida) diegensis Bartsch, which may be consid- 

 ered the type of the subgenus, and Cerithiopsis (CeritMopsida) 

 rowelli Bartsch. 



A fourth group, consisting of three species, has the early portion of 

 the nuclear turns smooth; the rest finely, axially ribbed, with the 

 intercostal spaces finely, spirally lirate. For these I would suggest 

 the subgenus CeritMopsidella, with Cerithiopsis (CeritMopsidella) 

 cosmia Bartsch as type. The other two species are Cerithiopsis 

 (CeritMopsidella) antejilosa Bartsch and Cerithiopsis (CeritMopsidella) 

 alcima Bartsch. 



The species in which the nuclear whorls are unknown are: 



excelsa Dall. antemunda Bartsch. 



curtata Bartsch. diomedeae Bartsch. 



fossilis Bartsch. wittiamsoni Arnold. 



gloriosa Bartsch. truncata Dall. 



columna Carpenter. stephensae Bartsch. 



infrequens C. B. Adams. montereyensis Bartsch. 



paramoea Bartsch. ingens Bartsch. 



arnoldi Bartsch. tumida Bartsch. 



bicolor Bartsch. peruviana D'Orbigny. 



magellanica Bartsch. destrugesi De Folin. 



Only five of the forty-four known species are fossils, and none, as 

 far as known, occur both recent and fossil. Of these five, two have 

 their nuclear characters well preserved and thus enable us to assign 

 them to their proper positions. These are Cerithiopsis (Cerithiopsis) 

 fatua Bartsch and Cerithiopsis (Cerithiopsina) necropolitana Bartsch. 

 Both of these are from the Pleistocene of San Pedro, California. The 

 other three species without the nuclear characters are Cerithiopsis 

 excelsa Dall, from the Eocene of Oregon; Cerithiopsis fossilis Bartsch 

 and Cerithiopsis wittiamsoni Arnold, from, the Pleistocene of San 

 Pedro, California. 



It is hoped that the present paper may stimulate the west American 

 collectors to be on the lookout for these charming little shells, and 

 that their efforts will result in a speedy elimination of the species now 

 referred to an uncertain position. 1 



1 In the preparation of the present diagnoses the following terminology is used: 



" Axial sculpture," the markings which extend from the summit of the whorls toward the umbilicus. 



The axial sculpture may be— 



"Vertical," when the markings are in general parallelism with the axis of the shell. 



" Protraetive," when the markings slant forward from the preceding suture. 



"Retractive," when the markings slant backward from the suture. 



"Spiral sculpture," the markings following the directions of the coils of the whorls. 



