SIPHONODENTALIUM. 137 



Norv., p. 103, pi. 7, f. 2 a-c, and pi. I, f. 2 (radula). VERRILL, 

 Trans. Conn. Acad. Sci., v, p. 557, pi. 42, f. 19 ; Proc. U. S. Nat. Mus., 

 iii,p.394. 



Siphodentalium vitreum M. SARS, JEFFREYS, Ann. Mag. Nat. Hist. 

 (4), xix, p. 155 (1877) ; P. Z. S., 1882, p. 662. 



Dentalium lobatum G. B. SOWERBY, JR., Thes. Conch., iii, p. 100, 

 f. 44(1860); Conch. Icon., xviii, pi. 5, f. 36 (1872). CLESSIN, 

 Conchyl. Cab., p. 15, pi. 4, f. 6 (1896). " D. labiatum Sow." in 

 Zoological Kecord for 1877, Moll., p. 79. 



The well-known name vitreum being preoccupied, we have been 

 compelled to substitute lobatum Sowerby, which applies to exactly 

 the same form, as Jeffreys and others have recognized. 



Jeffreys describes the soft parts as follows: " Body whitish, gela- 

 tinous, and nearly transparent ; mantle rather thick, forming a collar 

 round the foot ; tentacles thread-like, very slender, and having 

 obloug tips or bulbs ; they are not numerous, but extensile and irre- 

 gular in length, issuing from underneath the edge of the mantle : 

 foot cylindrical, extensile, and attaining a length equal to that of the 

 shell ; when at rest it is conical ; but the point fully stretched out 

 expands into a round and somewhat concave disk with serrated or 

 notched edges; excretal fold or tail at the narrowest end of the shell, 

 tubular, and having the front split open and exposed diagonally ; 

 edges jagged; externally covered with very fine and close set cilia; 

 liver dark-brown ; ovary lemon color." 



S. TYTTHUM Watson. PI. 23, fig. 2. 



Shell minute, very conical, i. e., broadening rapidly, much bent> 

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

 coming opaque when dead, and then also glossy but not brilliant. 

 Sculpture : some very faint traces of circular strise 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. 



Length 0'22 inch., breadth at mouth 0'049 ; at apex 0'013 inch. 

 (Watson). 



North of Culebra Island, West Indies, 390 fms. (Challenger). 



Siphodentalium tytthum WATS., Journ. Linn. Soc., xiv, p. 520 

 (1879) ; Chall. Rep., p. 14, pi. 2, f. 5. 



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

 broadens much faster and is more curved. (Watson). 



There is apparently no contraction toward the aperture. 



