44 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



DENTALIUM (ANIALIS) ANTILLARUM Orbigny. 



Plate 5, figs. 1, 2, 3, 4, 6, 7, 8. 



1846. Dentalium antillarum Orbigny, Moll. Cuba, vol. 2, p. 202, pi. 25, figs. 10-13. 



1887 (?). Dentalium antillarum, Simpson, Proc. Dav. Acad. Sci., vol. 5, p. 70. 



1897. Dentalium (Antalis) antillarum, Pilsbry and Sharp, Tryon's Man. Conch., 

 vol. 17, p. 57, pi. 14, figs. 22-25 (also probably figs. 16, 17, 18, 20, 21). 

 In part. [Not D. antillarum, Dall, Bull. Mus. Comp. Zool., vol. 9, p. 37 

 (1881) nor Dall, Bull. Mus. Comp. Zool., vol. 18, p. 421 (1889) nor Dall, 

 Bull. 37, U. S. Nat. Mus., p. 76 (1889 and 1903), all of which are Denta- 

 lium bartletti.] 



1901(?). Dentalium antillarum, Dall and Simpson, U. S. Fish Com. Bulletin for 

 1900, vol. 1, p. 456. [Not D. antillarum, Dall in Nat. Hist. Bull., State 

 Univ. Iowa (1896), vol. 4, No. 1, p. 20.] 



The shell is small, moderately curved, with its greatest curvature 

 in the extreme posterior position. The apex is rather blunt as it 

 quickly increases in diameter, but thereafter the shell exhibits an 

 even regular slow increase. The tip is sharp, slender, and strongly 

 curved, but it is very rarely retained. The surface is of an opaque 

 white color and sometimes reflects a greenish tint, and is always 

 encircled more or less distinctly by bands o[ translucent gray, observ- 

 able usually as translucent spots on the ribs. This is a very charac- 

 teristic feature, and is never wholly absent in fresh specimens. The 

 texture of the shell is hard, compact, and porcellanous, but not 

 shining. The sculpture consists of nine primary ribs, which are 

 almost at once increased by intercalation to 12. They may be either 

 well elevated or decidedly flattened, at first separating spaces of 

 double their own width; further intercalation of a secondary rib 

 between each ]>rimary soon takes place, thereby doubling the original 

 number and causing the ribs and the intercostal spaces to assume 

 about equal widths. The intercalated ribs attain equal importance 

 with the original ones, and all continue, though with decreasing 

 distinctness in senile specimens, to the anterior aperture. In some 

 specimens, however, but little intercalation takes place, the primaries 

 continuing alone to the maturer stages of the shell, when some lesser 

 secondary ribs usually appear. In such forms the primary ribs seem 

 more prominent, especially if they are not flattened, and thus impart 

 to the shell a somewhat different aspect. A further sculptural feature 

 is a system of exceedingly fine transverse lirae within the intercostal 

 spaces, which vary in degree from mere growth lines in some speci- 

 mens to clearly defined lirae in others. A wide shallow apical notch 

 on the convex, or more rarely on a curved side, is present. 



Average specimens measure: 



Length, 22 mm.; diameter, 2.1 mm.; arc, 2 (tip intact). 



Length, 27 mm.; diameter, 2.5 mm.; arc, 1.75 (tip gone). 



