EAST AMERICAlSr SCAPHOPOD MOLLUSKS. 65 



DENTALIUM (ANTALIS) BARTLETTI, new species. 



Plate 8, fig. 2, 7. 

 1881. Dentaliuvi antillarnm, Dall, Bull. Miis. Comp. Zool., vol. 9. p. 37 (not of 



Orbigny, 1846). 

 1889. Dentaliuvi ajitillarum, J) Ai.h, Bull. Mus. Comp. Zool., vol. 18, p. 421 (not of 



Orbigny, 1846). 

 1889. Dentaliuvi antillarum, Dall, Bull. 37, U. S. Nat. Mus., p. 76, in part. 

 1897. Dentaliuvi antillarnm, Pilsbry and Sharp, Tryon's Man. Conch., vol. 17, 



p. 57, in part. Not figured on pi. 14. 

 1903. Dentaliuvi antillaruvi, Dall, Bull. 37, U. S. Nat. Mus., p. 76 (in part). 



In the National Museum collection are a number of lots of long, 

 slender, slightly curved Dentalia, with very fine longitudinal riblets, 

 all collected from the continental slope zone. For the most part 

 these shells have been referred to Orbigny's D. antillarum. They all 

 bear the glazed aspect so characteristic of many deep-water Sca- 

 phopods, and they possess, moreover, no trace of any transverse 

 sculpture. They also belong to a deeper, colder water zone than 

 does Orl)igny's D. antillarum, which is a semilittoral species. The 

 following diagnosis is given from an excellent specimen taken off 

 Frederickstadt: 



The shell is very slightly curved, the chief curvature occurring 

 rather abruptly near the posterior end, quite thin; regularly increas- 

 ing in diameter to 4 mm. in a length of 42 mm. The color is ivory 

 white. The apical sculpture consists of about 18 thread-like riblets, 

 with smooth spaces between of double their own width. The ribs 

 continue to the posterior end in a shghtly wavy course, their original 

 primaries being greatly increased in number of intercalation of sec- 

 ondaries. At the oral end of the shell the ribs are 40 to 50 in num- 

 ber, but less distinct and are wider than their intervals. In the 

 anterior half minute growth lines to be seen under a lens interrupt 

 the longitudinal riblets, giving a roughened or wavy appearance to 

 the surface. The entire surface has a glazed ivory wliite finish. The 

 anal orifice bears a wide, fairly deep apical notch on the convex side. 

 The shell is slightly flattened laterally and the aperture is oblique. 



Length, 42 mm.; greater diameter, 3.75 mm.; lesser diameter, 3.5 

 mm.; arc, 1.7 (type). 



Length, 55 mm.; greater diameter, 4 mm.; lesser diameter, 4 mm.; 

 arc, 1.75 (tip gone). 



Length, 34 mm.; greater diameter, 2.5 mm.; lesser diameter, 2 

 mm.; arc, 1.1 (Florida specimen). 



Same variation is shown in the rate of increase of diameter. In a 

 specimen from 193 fathoms off Cape Florida the shell is much more 

 slender than the type, though preserving all other character of the 

 species. 



The type. Cat. No. 224986, U.S.N.M., was taken by the BlaJce at 

 the U. S. Coast Survey Station 130, off Frederickstadt, Santa Cruz, 

 in 451 fathoms, gray ooze, bottom temperature 44.5° F. 



