178 CADULUS-GADILA. 



a'. Stripe slight, shallow, less evenly developed; length 8 J 

 times the greatest diameter. striatus, p. 179. 



II. Shell smaller, not striated longitudinally. 



a. Species of stout or rather stout figure, the inflation mod- 

 erate or conspicuous, greatest diameter at the anterior 

 third or fourth of the length. 



b. Tube approaching circular in section at aperture 



and equator, californicus, p. 180 ; tolmiei, p. 181. 



b'. Tube markedly flattened at aperture and equator, 



platy stoma, p. 180. 

 a'. Very slender species, with the slight inflation anterior, 

 contraction toward the mouth very short ; diameter con- 

 tained 7-10 times in the length. 



b. Shell smooth throughout ; anterior contraction 

 slight. 



c. Length 13'5 mill., 10 times the diam., 



aberrans, p. 193. 

 c'. Length lO'B mill., about 9 times the diam., 



fusiformis, p. 193. 

 c". Length 10 mill., about 7 times the diam., 



hepburni, p. 194. 

 b'. Shell circularly corrugated near the apex, 

 jierpusillus, p. 190 ; panamensis, p. 191; major, p. 192. 



C ALBicoMATus Dall. PL 35, fig. 15. 



Shell resembling C. spedabilis Verrill, but larger, with a less 

 prominent equator, more compressed in an antero-posterior direc- 

 tion, and with the anal opening produced at the sides and roundly 

 excavated in front and behind instead of notched laterally and pro- 

 duced medianly. Color milk-white ; incremental sculpture indi- 

 cated only by more or less translucent rings in the shell substance ; 

 longitudinally sculptured by extremely fine sharp grooves with equal 

 interspaces, ivhich cover the whole of the shell ; curvature moderate, 

 nearly uniform, slightly more marked near the anal end ; the whole 

 shell distinctly compressed, though not flattened, except below the 

 oval aperture, where the shell is impressed, making a shallow sul- 

 cus extending backward nearly two millimeters, and in front arch- 

 ing the margin so that the perfect aperture is distinctly uniform 

 with sharp, thin edges. There is no swollen equatorial girdle ; the 

 greatest diameter is near the posterior end of the above-mentioned 



