CADULUS-POLYSCHIDF.S. 149 



western Atlantic, extending off the east coast of the United States 

 to the island Fernando Noronha off Brazil, and with one representa- 

 tive in the Pacific (California). The Atlantic forms differ from one 

 another only in size and length of the teeth ; and seem to us to be 

 merely local races or subspecies rather than of specific rank. As 

 others may prefer to retain the several forms as species, we give be- 

 low full information upon them with the original diagnoses. 



Var. QUADRIDENTATUS (Dall). PI. 23, fig. 7 ; pi. 28, figs. 1-5. 



Shell moderately arcuate, the bend greater posteriorly, not much 

 tapering ; milky-bluish, glassy, smooth, the growth striso very slight ; 

 gradually increasing to a point quite near the aperture, thence 

 slightly contracted. Greatest diameter contained about 7 times in 

 the length of shell. Tube nearly circular in section, slightly com- 

 pressed vertically. Aperture very oblique, transversely oval. Apex 

 cut into four rather conic teeth, which toward their points are 

 bevelled at the outside edges, by four deep slits ; the tooth on con- 

 vex side longest, the other three subequal in length, that on the con- 

 cave side widest and obtuse. 



Length 975, diam. at aperture I'O xl'l ; diam. at largest l'32x 

 1*38; diam. at apex 0'75 x 0*76 mill, (specimen from Florida 

 Strait). 



Largest specimen of a series from off Cape Fear, 9 mill, long ; 

 smallest adult 6 - 6 mill. 



Bermuda (Heilprin) ; Cape Hatteras (U. S. F. C., Rush) south to 

 west coast of Florida, 30 fins. (Pourtals) ; Fernando Noronha; and 

 mouth of the Rio la Plata, in 10\ fms. (U. S. Fish Commission) ; 

 Pliocene of Caloosahatchie River, Florida. 



The differences between C. tetraschistus, C. quadridentatus and C. 

 incisus seem to be pretty well covered by the variations observed 

 among individuals dredged off the southeastern U. S. We do not 

 see that there is any considerable or sufficient difference, when the 

 measurements of all are compared. C. quadridentatus may be con- 

 sidered a large race or subspecies, and C. incisus a form intermedi- 

 ate between the two extremes. As to contour, they are all prac- 

 tically alike. The specimen figured by Dall has the teeth abnor- 

 mally obtuse, probably from old age and wear. Watson's figure of 

 tetraschistum does not show the tooth on convex side as long as it is 

 in perfect North American specimens. We repeat here Dall's 

 original description, and give a copy of his figure, pi. 23, fig. 7. 



