58 DENTALIUM-ANTALIS. 



unequal, fewer by loss of those intercalated in the interstices, and the 

 remaining ribs, about 20 in number, are alternately large and small 

 (and in younger shells there are 10 strong ribs). Aperture circular. 

 Anal orifice small, ovate with thick walls, and a wide, shallow tri- 

 angular notch on the convex side. 



Length 23*5, diam. of aperture 2*5, of apex 1*3 mill. 



Length 22*5, diam. of aperture 2'3, of apex 0*9 mill. 



Entire West Indies and Gulf of Mexico ; north in deep water to- 

 Cape Hatteras. Barbados, Dominica, Martinique, St*. Vincent, Gren- 

 ada, Santa Cruz, Arrowsmith Bank, Yucatan, and Yucatan Strait; 

 of Cuba; off Cape Fear, N. C. (Blake and Albatross) ; Off Cape 

 Hatteras (Rush), 17-1000 frns., Pourtales plateau (Iowa S. U. Bahama 

 Exp.) ; St. Martin, Saba and Key West, Florida (Acad. coll.) ; St. 

 Thomas (Orbigny). 



D. antillarum ORB., Moll. Cuba, ii, p. 202, pi. 25, f. 10-13 (1842 

 or 1846). DALL, Bull. M. C. Z., ix, p. 37 (1881); Ibid, xviii, 

 Blake Rep., p. 421 (1889) ; Nat. Hist. Bull. State Univ. Iowa, iv, 

 no. 1, p. 20. 



The riblets on the larger portion of the tube are much more equal 

 and less coarse than in D. disparile Orb., a species often occurring- 

 with this one, and of equally wide distribution. d'Orbigny's descrip- 

 tion and figures were from a young specimen. 



Dall writes as follows : This well marked species is uniformly 

 finely grooved from the tip to the anterior part, the interspaces being 

 rounded, subequal, and thread-like, growing slightly finer anteriorly. 

 The section is circular, the notch is on the convex side, shallow and 

 wide, often decollate. I believe its range extends north to New Eng- 

 land, and possibly to Nova Scotia, in deep water, judging by spec- 

 imens so labelled in the National Museum. 



D. TAPHRIUM Dall. 



Shell short, stoutish, slightly curved, pale apple-green, which is so- 

 alternated in ill-defined zones of translucency and opacity as to give 

 on a fresh specimen the effect of the silk known as moire antique, 

 though the sculpture is not modified in these zones ; sculpture of 

 very fine sharp slightly elevated incremental lines, visible only in 

 the interspaces between the longitudinal threads ; the latter are 

 even, squarish, rather flattened threads, with subequal channelled 

 interspaces, about six threads to the millimeter of circumference ;. 

 close to the aperture they become faint, and posteriorly every alter- 



