128 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



In that the shell of this species is slightly compressed laterally, its 

 position is next to Cadulus lunula. It has a slightly larger shell than 

 C. hushii and is again distinguishable from that species by its lateral 

 compression — hushii having a very noticeable dorso-ventral com- 

 pression. It is named for Mr. Charles T. Simpson, the joint author 

 with Doctor Dall in the report upon the Porto Rican mollusks, 

 referred to above. 



CADULUS (PLATYSCHroES) AMIANTUS Dall. 



Plate 19, fig. 8. 



1881. Cadulus sauridens, Dall, Bull. Mus. Comp. Zool., vol. 9, p. 36 (not of Wat- 

 son, 1879). 



1889. Cadulus amiantus BAhL, Bull. Mus. Comp. Zool., vol. 18, p. 431, pi. 27, 

 fig. 7, in part. 



1889. Cadulus ajniantus Dall, Bull. 37, U. S. Nat. Mus., p. 78, pi. 27, fig. 7, in 

 part. 



1898. Cadulus (Gadiln) amiantiis, Pilsbry and Sharp, Tryon's Man. Conch., vol. 

 17, p. 174, pi. 25, fig. 52, in part. 



1903. Cadulus amiantus Dall, Bull. 37, U. S. Nat. Mus., p. 78, pi. 27, fig. 7, in 

 part. (Not C. amiantus, Dall and Simpson, in Bull. U. S. Fish Commis- 

 sion for 1900, p. 457.) 



Th€ type of this species is a young and somewhat defective speci- 

 men that will not admit of the careful description these difficult little 

 shells require. The only description given is a comparison of the 

 shell with Doctor Watson's Cadulus sauridens and C. vulpidens, 

 neither of which species do we know in this country save by the origi- 

 nal descriptions. A careful comparison of the type with all the west- 

 ern Atlantic species of the group has resulted only in doubt and 

 confusion owing to the imperfections of the type itself. The shell is 

 smaller than any of the group except C. nitidus, which is more slender. 

 Its nearest ally is C. miamiensis, which in turn is somewhat larger. 

 The following supplemental diagnosis is given from the type of C. 

 aTYiiantus: 



The shell is small, moderately curved, slender, with its section of 

 maximum diameter about two-fifths distance from the anterior end ; 

 this does not amount to a local swelling, nor is the equator angled. 

 The convex side presents an even uninterrupted arc, of which the 

 anterior portion is somewhat flattened. The coftcave side has its 

 greatest arc in the posterior third, its anterior half being almost 

 straight with a slight convexity opposite the equator. From the 

 equator on the convex side to the anterior aperture the cylinder is 

 flattened very perceptibly, the balance of the shell being round. 

 The larger aperture is oblique. The apical orifice is round and 

 is neither very large or very small. The apical features show some 

 modification from a simple rim, but no clear diagnosis can be made. 



The type is in the collection of the Museum of Comparative Zoology, 

 Cat. No. 7749, and measures — length, 5.75 mm.; diameter, 1.04 mm. 



