520 RET. U. BOOG WATSON ON THE 



closely tliau with the S. pentagonum, Sars. Here, however, the 

 longitudinal ribs are much closer, as well as much more obsolete ; 

 the shell is more curved throughout its whole length, is more 

 attenuated, and retains its square form and sharp angles instead df 

 becoming rounded as in S. tetragonum, Brocchi. Amidst all the 

 variations of that very variable form I have not seen any that 

 connects it with this species. 



2. SiPHODENTALIUM TYTTHUM, W. {tvtQos.) 



St. 24. March 25, 1873. Culebra Island, St. Thomas, 



D. W. I. 390 fms. Mud. 4 specimens. 



Shell. — Minute, very conical, i. e. broadening rapidly, much bent, 

 very thin, but not hyaline, apparently horny when living, and 

 becoming opaque when dead, and then also glossy but not 

 brilliant. Sculpture. Some very faint traces of circular striae on 

 the lines of growth. Mouth-edge very thin and chipped. Apex 

 broken, but in one specimen showing the two lateral clefts 

 common in the genus. L. 0*22. B. at mouth 0"049, at apex 

 0-013. 

 In texture and in general form this is like S. vitreum, Sars, but 



it broadens much faster and is more curved. 



3. SlPHODENTALIUM PUSILLTJM, W. (pusUlltS.) 



St. 85. July 19, 1873. Lat. 28° 42' N., long. 18° 6' W. Palma, 

 Canaries. 1125 fms. Volcanic sand. 2 specimens. 

 Shell. — Minute, attenuated, slightly bent, thin, transparent, ir- 

 regularly banded with opaque white, which runs elliptically 

 round the shell. Sculpture. There is no trace of longitudinal 

 striae, but the whole surface is sharply scratched with minute 

 transverse strise, which run (as usual) not directly round the shell, 

 but advance on the concave and retreat on the convex curve. 

 L. 0-12. B. at small end O'Ol, at broad end 0-02. 

 These specimens are both young, and both ends are chipped. 

 It is straighter and more tumid than Siphodentalium minutwn, 

 H. Ad. (Grulf of Suez, MacAndrew), and not contracted at the 

 mouth. It is also straighter and more tumid than D.filum, Sow. 

 (in part), =^roc«7e, JefFr., Journ.de Conch. 1872, p. 140, v. 5, but 

 more cui'ved and broader than the young of _D. capillosum, JefFr. 

 It is much larger, more tumid, and straighter for the same length 

 than Siphodentalium lofotense, Sars. 



