568 



bartsch: northwest coast mollusks 



Five species of Caecum are known living on our Pacific shores north 

 of San Diego. Four of these are undescribed. Some of the unnamed 

 forms have at times been Hsted under names bestowed by Carpenter 

 and Adams upon species occupying a more southern habitat. Three 

 of these five species, Caecum californicum, C. dalli and C. grippi are 

 robust forms and are much larger than the other two, C. licalum and 

 C. diegense. Caecum californicum is larger than C. dalli and C. grippi 

 and has about forty strong annuli, separated by narrow spaces, while 

 C. dalli and C. grippi are of about the same size ; the former has about 

 twenty annuli on the last segment, while the latter has only about 

 fifteen. While the annuli are of almost the same width, the spaces 

 between them are much wider in C. grippi than in C. dalli. Caecum 

 licalum has about eighteen broad annuli, while in C. diegense about 

 twenty narrow slender rings are present. 



TABLE 2 

 Additional Data Pertaining to the Above Caecums 



Caecum dalli, sp. nov 



Caecum grippi, sp. nov. . . , 

 Caecimi licalum, sp. nov. . 

 Caeciun diegense, sp. nov. 

 Caecimi californicum Dall. 



Height 

 in mm. 



2.5 

 2-3 

 2 .2 

 2 .0 

 2.8 



Diameter 

 in mm. 



0.7 

 0.7 



0.5 

 0.4 

 0.8 



Type 

 locality 



San Diego. 

 San Diego. 

 San Diego. 

 San Diego. 

 San Diego. 



Caecum californicum Dall is the most abundant West American 

 Caecum. It is known from many stations from Monterey, California, 

 to Lower California. C. dalli Bartsch is known from many stations 

 from San Diego to Lower California, C. licalum Bartsch from San 

 Pedro and San Diego. C. diegensis Bartsch has only been reported 

 so far from the littoral zone at San Diego. C. grippi Bartsch was 

 dredged in 15-20 fathoms off' San Diego. 



Micranellum, gen. nov. 



Surface of the shell marked by closely spaced, slender, axial annula- 

 tions; operculum thin, corneous, concave. Type Caecum crebricinctum 

 Carpenter. 



Seven species of Micranellum are known living in northwestern 

 America. Five of these have the plug at the truncated apex forming 

 an attenuated, obliquely placed spur, the base of which is narrower 



