EAST AMERICAN SCAPHOPOD MOLLUSKS. 27 



DENTALIUM (DENTALIUM) TEXASIANUM Philippi. 



(?)1848. Dentalium americanum Chenu, Conch. III., vol. 1, p. 1, pi. 4, figs. 9, 10 (all 



subsequent references in European literature). 

 (?)1843. Dentalium americanum var. c, Chenu, Conch. 111., vol. 1 (index), pi. 6, fig. 

 35 (not pi. 4, figs. 9, 10). 

 1848. Dentalium texasiana Philippi, Zeitschr. Malak., p. 144. 

 1878. Dentalium sexangulare Hilgard and Hopkins, Report Borings Miss. River, 

 and Lake Borgue, Engineer's Dept., U. S. A., p. 48, pi. 3, fig. 7 (not of 

 Lamarck). 

 1889. Dentalium gouldii Dall, Bull. Mus. Comp. Zool., vol. 18, pt. 2, p. 424 (not 



pi. 27, fig. 4), in part. 

 1889. Dentalium gouldii Dall, Bull. 37, U. S. Nat. Mus., p. 76, in part (not fig.). 



1896. Dentalium gouldii Guppy and Dall, Proc. U. S. Nat. Mus., vol. 19. p. 

 325, in part. 



1897. Dentalium {Dentalium) texasiana, Pilsbry and Sharp, Tryon's Man. of 



Conch., vol. 17, p. 22. 

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



20 (not pi. 7, fig. 14), in part. 

 1903. Dentalium gouldii Dall, Bull. 37, Reprint, U. S. Nat. Mus., p. 76, in part. 



The following essential features are taken from topotypes in the 

 National Museum collection. 



The shell is rather strongly curved in the posterior portion, but less 

 so anteriorly; very slowly increasing in diameter. It is hexagonal in 

 section; dull gray- white in color, not glassy or porcellanous, but 

 opaque, solid and strong. The tip is hexagonal, the angles soon 

 becoming narrow rod-like ribs, separated by wide, flat interspaces, 

 smooth save for ill-defined widely separated growth lines or wrinkles. 

 Intercalation of one or two, rarely three, longitudinal riblets may or 

 may not take place. The ribs persist to the end, though less definitely 

 marked anteriorly, but the sheU often preserves the hexagonal sec- 

 tion throughout. When greater intercalation is present the hexagonal 

 section is less obvious at the oTal aperture. In senile specimens all 

 sculptural features may be almost lost at the extreme anterior end 

 the shell then becoming a roughly rounded cylinder. The growth 

 lines are more prominent in the anterior portion of the shell, almost 

 attaining the importance of transverse sculpture. The apical char- 

 acters remain doubtful; none of the museum specimens show either 

 notch or slit. Many specimens have a projecting tube from the 

 posterior orifice, but this is not a specific character. 



Length, 31 mm., diameter, 2 mm. (composite specimen made up of 

 tip and fragment), Sanibel Island, Florida. 



Length, 21 mm.; diameter, 2 mm.; arc, 1.5, Sanibel Island, Florida 

 (without tip). 



Topotypes, Cat. Nos. 125552 and 1.34447, U.S.N.M. (Galveston). 

 157582°— 20 3 



