EAST AMERICAN SCAPHOPOD MOLLUSKS. 



49 



the Greater Antilles, the east coast of Florida, or Hatteras. It is 

 apparently confined to the littoral zone. 



Most commentators appear to have fallen into some error in the 

 consideration of this species, generally confusing it with Dentalium 

 antillarum. Orbigny's description is short and leaves much to be 

 desired, but his figure, though of a juvenile specimen, is excellent. It 

 is less closely related to D. antillarum than it is to Z), texasianum and 

 to a Pliocene group represented by D. coloosaense Dall, D. prisma 

 Dall, and D. octocostellatus Pilsbry and Sharp. It might with equal 

 propriety be placed under Dentalium s. s. 



The following are the five records in the museum collection : 



Num- 

 ber of 

 speci- 

 mens. 



Cat. No. 

 U.S.N.M. 



Locality 



61018a 



93833 



225819 



150784 



18711 



Remarks. 



Tampa Bay, Florida (Simpson). 



Sabanilla, West Indies Shore (Hering). 



San Sebastian, Brazil 



do 



Rio Janerio 



United States Exploring Expedi- 

 tion. 



KEY TO THE GROUP OF DENTALIUM CERATUM. 



Tip 9 angled. 



Smooth posterior portion ])rodiicecl. 



No intercalation on tip Dentalium ceratum ceratum, page 50. 



Intercalation on tip (to 12 or 14). 

 Color yellow. 



Diameter of 2 mm. (Florida) D. ceratum flavum, page 51. 



Diameter of less than 2 mm. (Barl)ados)..Z). ceratum tenax, page 52. 

 Smooth posterior portion not jiroduced. 



Color green D. taphrium., page 53. 



DENTALIUM (ANTALIS) CERATUM Dall. 



1881. Dentalium, ceratum Dall, Bidl. Mus. Comp. Zool., vol. 9, p. 38. 



1889. Dentalium ceratum Dall, Bull. Mus. Comp. Zool., vol. 18, p. 424, pi. 26, fig. 



5; pi. 27, fig. 2. 

 1889. Dentalium ceratum Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 26, fig. 5. 

 1897. Dentalium ceratum, Pilsbry and Sharp, Tryon's Man. Conch., vol. 17, p. 



57, pi. 7, figs. 4, 5. 

 1903. Dentalium ceratum Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 26, fig. 5. 



The shell is awl-shaped, with the chief curvature in the tip or ex- 

 treme posterior portion, the balance of the shell having a relatively 

 small arc. In color it is of a waxen yellow ranging from a brilliant 

 yellow in some specimens, especially in the posterior half, to a pale 

 yellowish tint becoming white in the anterior half of the shell. The 

 texture of the shell is glassy, with a polished shining surface. The 

 tip is nine ("seven") angled in section. The angles forming nine pri- 

 mary rodlike riblets narrow and sharply defined and separated by 



