58 



BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



floor. The Argentine record consists of but broken fragments, though 

 recognizable. The depth of 11 fathoms, as given at this Argentine 

 station, suggests an error as already commented upon. 

 The following are the museum collection records: 



I Type. 

 DENTALIUM (HETEROSCHISMA) SUBTERFISSUM Jeffreys. 



Doctor Watson has referred to this European species of Jeffrey's 

 some specimens taken by the Challenger at Station 120 off Pernam- 

 buco in 675 fathoms.^ I am inclined to believe that these specimens 

 are probably referable to Doctor Dall's callitJirix rather than to the 

 northeast Atlantic species of Jeffreys. In the present state of doubt 

 I include it in this list only as a possible member of the faunal area 

 under discussion. 



Subgenus FISSIDENTALIUM Fischer, 1895. 



1895. Fissidentalium Fischer, Manuel de Conchyliologie, p. 894. 



"A long fissure on the convex side in the posterior portion of the 

 shell; surface longitudinally striate." Pilsbry and Sharp ^ have ex- 

 panded this very meager description to include a series of very large 

 solid shells with very many longitudinal riblets and with or without 

 a long slit at the apex. The value of the subgenus is \rery doubtful. 

 The western Atlantic species included in this paper are Dentalium 

 meridionale with its several subspecies, D. Jloridense, and D. ampJiia- 

 lum- — all Dentalia with large shells and belonging to rather deep 

 water zones. The following key is not very satisfactory, but may 

 aid in separating the forms: 



1 Challenger Report, Gastropoda and Scaphopoda, p. 10. 



2 Tryon, Man. Conch., vol. 17, p. 63. 



