EAST AMERICAISI SCAPHOPOD MOLLUSKS. 



43 



DENTALIUM (ANTALIS) OCCIDENTALE GEORGIENSE, new name. 



Plate 5, fig. 5. 



1884. Dentalium occidentalis sulcatum Verrill, Trans. Conn. Acad, of Arts and 

 Sci., vol. 6, p. 217 (not of Lamarck, 1818, nor of Sacchi). 



1884. Dentalium. occideyitalis sulcatum Verrill, Report of Com. of Fish and Fish- 

 eries for 1883, p. 573. 



1897. Dentalium occidentalis sulcatum, Pilsbry and Sharp, Tryon's Man. Conch., 

 vol. 17, p. 48. 



1915. Dentalium occidentalis sulcatum, Johnson, Occ. Papers Boston Soc. Nat. 

 Hist., vol. 7, p. 83. 



This is a form characterized by a greater definiteness of sculpture 

 upon the shell and which assumes the importance of very well marked 

 riblets, with concave grooves between, and further having its sculp- 

 tural features extend through to the interior of the shell. This is 

 owing to a lesser thickness of its middle or chalky layer. The shells 

 are of a thinner, harder texture, and therefore resist erosion. It is 

 connected with the typical subspecies by intermediates. Verrill's 

 type is not in the museum collection, but there are five lots from his 

 hands from off Georges Bank, and off Marthas Vineyard. One lot 

 from off Marthas Vineyard in 67 fathoms is the least recorded depth. 



The specimen figured on plate 5 is from a lot of two examples, Cat. 

 No. 52742, U.S.N.M., dredged by the Albatross at theU. S. B. F. Sta- 

 tion 2582, off Marthas Vineyard, in 137 fathoms, green mud, bottom 

 temperature 47.2°. It measures — length, 29 mm.; diameter, 3.5 

 mm.; arc, 2. 



KEY TO GROUP OF DENTALIUM ANTILLARUM. 



Shell with nine primary ribs. 



Color plan of translucent spots present. 



Microscopic sculpture present Dentalium antillarum, page 44. 



Color plan of translucent spots absent. 



Microscopic sculpture absent , D. pseudohexagonum, page 46. 



157582°— 20 4 



