EAST AMERICAN SCAPHOPOD MOLLUSKS. 23 



Tip section not hexagonal. 



Primary ribs 9 obscurum, page 32. 



Primary ribs more than 9. 



Intercostal sculpture of transverse riblets carduus, page 33. 



Intercostal sculpture of latticed design laqueatum, page 23. 



Sculpture becoming obsolete near aperture Jagwrnium laqueatum, page 24. 

 Sculpture not becoming obsolete near aperture. Za^^/eaitim regulare, p. 26, 



DENTALIUM (DENTALIUM) LAQUEATUM Verrill. 



1885. Dentalium laqueatum. Verrill, Trans. Conn. Acad. Arts Sci., vol. 6, pt. 2, 



p. 431, pi. 44, fig. 18. 

 1889. Dentalium laqueatum, Dall, Bull. Mus. Comp. Zool., vol. 18, pt. 2, p. 426, 



pi. 27, fig. 1. 

 1889. Dentalium. laqueatum, Dall, Bull. 37, U. S. Nat. Mus., p. 78, pi. 27, fig. 1; 



pi. 46, fig. 18. 

 1897. Dentalium (Dentalium) laqueatum, Pilsbry and Sharp, Tryon's Manual of 

 Conch., vol. 17, p. 10, pi. 7, figs. 1, 2; pi. 5, fig. 73. 



The shell is large with a maximum length and diameter of 62 by 

 6^ mm., rather thick, strong, gently curved, the tip being sharply 

 curved. The tip is nine angled, quickly tapering; the balance of 

 the shell only moderately so. Adult specimens are always without 

 tips. Occasionally the shell is slightly flattened dorso-ventrally. 



The color is dull white, opaque, neither glassy nor chalky. Nearly 

 all the National Museum specimens are black stained on the poste- 

 rior portion of the shell. 



The sculpture consists of 9 to 12 strong elevated primary longi- 

 tudinal ribs, with about equally spaced concave intercostal spaces. 

 The ribs become broader and less elevated in about the middle por- 

 tion of an adult shell, while the spaces between them become wider 

 and flatter, with but slight intercalation of less important secondary 

 ribs. On the anterior third the ribs degenerate into a rather smooth 

 surface, or sometimes persist to the aperture. Over all the shell 

 surface, including the ribs, is spread a fmely reticulated sculpture, 

 becoming only less apparent on the extreme anterior portion, or 

 where worn off on the rib summits. 



An apical notch on the convex side sometimes extends into a 

 fairly long slit, but these apical characters are often quite obliterated. 



Length, 45 mm., diameter, 6 mm. (Verrill, type). 



Length, 51 mm., diameter, 6 mm., arc 1 (without tip). 



Length, 55 mm., greater diameter, 6 mm., lesser diameter, 5.5 mm. 



Length, 62 mm., greater diameter, 6.5 mm., lesser diameter, 6.5 

 mm.; arc, 1.5 (no tip). 



Tips are easily recognizable, aside from their sculpture, by rapid 

 increase in diameter, their sharp curve and the fluted peristome, 

 the primary sculptural features being repeated on the inside of the 



