EAST AMERICAlsr SCAPHOPOD MOLLUSKS. 75 



DENTALIUM (LAEVmENTALIUM) PERLONGUM Dall. 



Plate 9, fig. 1. 



1878. Dentalium perlongum Dall, Bull. Mus. Comp. Zool., vol. 5, No. 6, p. 61 



(name only). 

 1881. Dentalium perlongum Dall, Bull. Mus. Comp. Zool., vol. 9, p. 36. 



1888. Dentalium perlongum, Agassiz, Three Cruises of the Blake, vol. 2, p. 76, 



fig. 284. 



1889. Dentalium perlongum Dall, Bull. Mus. Comp. Zool., vol. 18, p. 419, pi. 



27, fig. 6. 

 1889. Dentalium perlongum Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 27, fig. 6. 

 1889. Dentalium perlongum Dall, Proc. U. S. Nat. Mus., vol. 12, p. 294. 

 1897. Dentalium. (Laevidentalium) perlongum, Pilsbry and Sharp, Try<m's Man. 



Conch., vol. 17, p. 104, pi. 18, figs. 10, 11. 

 1903. Dentalium perlongum Dall, Bull. 37, U. S. Nat. Mus.. p. 76, pi. 27, fig. 6. 



The shell is extremely long and slender, but slightly arched or 

 almost straight, thin but strong, slowly and regularly increasing in 

 diameter, with round section, and possessing a long needle-like 

 tip. It is opaque white, with a glossy, rather porcellanous but 

 not highly polished surface. Dead specimens take on a light brown- 

 ish gray or slate color. It is wholly sculptureless, save for some 

 excessively line longitudinal scratches on the tip and posterior por- 

 tion, only observable by aid of a lens but more often lacking even in 

 perfectly fresh specimens. Otherwise it is a perfectly smooth cylinder 

 barring the unimportant growth irregularities. A shallow to rather 

 deep apical notch on the convex side is present in normal speciniens. 

 The measurements are : 



Length, 90 mm.; diameter, 3.75 mm.; arc, 2 (tip gone). 



Length, 54 mm.; diameter, 3 mm.; arc, 1.2 (tip gone). 



A perfect adult specimen would exceed 100 mm. in length, with a 

 diameter of under 4 mm. 



The type is not in United States National Museum collection. 



A defective specimen from 20 fathoms southeast of Cape St. 

 Roque, Brazil, and some fragments from off Rio de la Plata, in 11 ^ 

 fathoms, seem to be referable to this species. 



The extreme length, slenderness, and straightness of this shell 

 set it apart from any other species of the western Atlantic. 



The following lots are in the museum collection: 



157582°— 20 6 



