98 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



1898. Cadulus (Polyschides) tetraschistus incisus, Pilsbry and Sharp, Tryons 



Man. Conch., vol. 17, p. 150, pi. 25, fig. 65. 

 1903. Cadulus quadridentatus Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 27, fig. 5. 

 1903. Cadulus incisus, Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 41, fig. 20. 



The shell is gradually and regularly increasing in diameter without 

 any local bulge or swelling to a section just back of the aperture, 

 thence it slightly contracts; moderately curved. A section of the 

 shell is nearly a circle. The aperture is very oblique, oval, with its 

 peristome rounded and smooth. The apex is cut by four deep slits, 

 leaving four pointed lobes; the longest on the convex side is often 

 a little bent in; the other three lobes are one on the ventral and two 

 on the lateral sides; the lateral ones are of subequal length; the 

 ventral lobe is wide and obtusely pointed. The edges of all these 

 triangular lobes are flattened as though planed off. 



Length, 10 mm.; greater diameter, 1.03 mm.; anterior aperture, 

 0.8 mm.; apical aperture, 0.4 mm. (type). 



Length, 8 mm.; greater diameter, 1.1 mm.; anterior aperture, 

 1 mm.; apical aperture, 0.5 mm. (type of C. incisus). 



Length, 7 mm,; greater diameter, 1 mm,; anterior aperture, 0,8 

 mm,; apical aperture, 0,5 mm, (C. incisus). 



Length, 8 mm,; maximum diameter, 1,10 mm,; anterior aperture, 

 1 mm.; apical aperture, 0.6 mm. (average). 



Length, 5.1 mm.; maximum diameter, 0.75 mm,; anterior aper- 

 ture, ,6 mm.; apex, .4 mm. (C. q. acompsus). 



The type of Cadulus quadridentatus is in the Museum of Compara- 

 tive Zoology (Cat. No. 7739) and is from the west coast of Florida, 

 in 30 fathoms, collected by Pourtales. 



The type of C. incisus, Cat. No. 44860, U.S.N.M., was dredged at 

 the U. S. Bureau of Fisheries Station 2272, off Cape Hatteras, in 15 

 fathoms, bottom of gray sand. 



The differences to be noted in Miss Bush's description of C. incisus 

 from that of Doctor Ball's C. quadridentatus are at once harmonized 

 by the comparison of many specimens. It is a very abundant shal- 

 low-water form from Cape Hatteras to the Gulf of Mexico, the Baha- 

 mas, Cuba, Yucatan, and probably throughout the entire Caribbean 

 region. It is also recorded from Bermuda. Two poor specimens 

 from off Rio de la Plata in 10 fathoms (Albatross Station 2765) seem 

 to be referable to this species. The deepest record in the Museum 

 collection is 52 fathoms off Cape Lookout, the least, 3 fathoms off 

 Miami, Florida, and off Cat Cay, Bimini Islands. 



Pilsbry and Sharp united this species with Watson's C. tetraschistus 

 as Doctor Dall had already suggested in his original description. 

 The ruling is probably correct, but lacking opportunity actually to • 

 compare specimens I hesitate to unite shallow-water forms separated 

 by so wide an expanse of deep sea. It is, however, a species of excep- 



