134 



BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



The following six species fall witliiii the Group 2, referred to under 

 the description of the subgenus Giiila; they all have small or very 

 small slender shells of median or submedian equator: Cadulus min- 

 usculus, 0. iota, C. suhuli,, 0. verrilli, C. regularis, C. atlanticus. 



CADULUS (GADILA) MINUSCULUS DaU. 



Plate 19, fig. 4. 



1889. Cadulus minusciihis Dall, Bull. Mu?. Comp. ZdoL, vol. 18, p. 432. 



1889. Cadulus minuscMlus Dall, Bull. 37, U.S. Nat. Mus., p. 78. 



1898. Cad'ilus (Gadila) minuscidus, Pilsbry and Sharp, Tryon's Man. ConcL., 



vol. 17, p. 164, pi. 32, fig. 42, 43. 

 1903. Cadulus minusculus Dall, Bull. 37, U. S. Nat. Mus., p. 78. 



The shell is very small, fusiform, slightly curved, with a moderate 

 swelling at a median equator; the anterior aperture is oblique, with a 

 rounded peristome; the apical orifice is round, and has an internal 

 translucent ring, about half the diameter of the aperture. The cyl- 

 inder is slightly compressed. The convex outline is rather strongly 

 arched but the concave outline is nearly straight with a slight con- 

 vexity at the equator. The lateral outlines are arcuate. No apical 

 features observable. Measurements are: 



Length, 2. .33 mm.; diameter, 0.616 by 0.58 mm.; anterior aperture, 

 0.34 mm.; apical aperture, 0.3 mm. (Pilsbry.) 



A very slight range in measurement is noted. 



The type, Cat. No. 93122, U.S.N.M., was obtained at the U. S. B. F. 

 Station 2595, off Cape Hatteras, in 63 fathoms, bottom of gray sand 

 and broken shells. 



The very small size of these tiny mollusks, permitting them to slip 

 through the meshes of any but very fine sieves, probably accounts for 

 the single record from a region of so many dredging stations. 



cadulus (GADILA) IOTA, new species. 



Plate 19, fig. 2. 



1901. Cadulus minusculus, Dall and Simpson, Bull. U. S. Fish Comm., vol. ] 

 for 1900, p. 457 (not minusculus Dall, 1889). 



The shell is very minute and somewhat swollen in its middle portion. 

 The convex outline is regularly arched ; the concave outline is almost 

 straight, with a slight convexity at a median equator and with a 



