some new and peculiar MoUusca. 155 



Station 12, 14/30 fnis. ; a ira;^mcnt only, but cvidcntlv" 

 belonging to this species, which I iiave described from speci- 

 mens taken in the 'Porcupine' and 'Challenger' Expeditions. 

 ' Poreuj)ine ' Expedition, 1801), off the west coast of Ireland, 

 118U-147() fins. 'Challenger' Expedition, lat. 37° 20' N., 

 long. 4.3^ 14' W., 1()0<) fnis. 



The slit in D. suliterjisHum is on the under or ventral side 

 of the shell, being the same position as in the D. inversum of 

 Deshayes, and the reverse of that in his D. rubescens and in 

 D. ensiculus. The organization of the animal is unknown ; 

 but D. iiirersum may be the t}i)e of a distinct gcims. 



A single and dead specimen of another shell, ap])arently 

 belonging to the genus Dentalium, occurred in Station 16, 

 1785 fathoms. It is narrowly cylindrical, rather solid, glossy, 

 smooth, and a quarter of an inch long. Its peculiarity con- 

 sists in the jiosterior termination forming a second and nar- 

 rower cylinder, which issues out of the larger and longer one, 

 as if from a sheath. This ])rocess has an entire and circular 

 point ; so that the shell cannot be a species of Siphodentalium. 

 I proj)ose to name it DeuUdium vagiaa. Perhajjs two imper- 

 fect specimens of a Dentalium from Station 12, 1450 fathoms, 

 may belong to the same species. 



SlPHONODENTALIUM, M. Sars. 



In the 'Journal de Conchyliologie ' for 1874, p. 258, the 

 Marquis di ^lontero.sato proposed the abbreviation of this ge- 

 neric name to Sijihodentalium ; and I agree with him that it 

 would be convenient. 



Siphodentalium vitreunij M. Sars. 



Dentalium vifreiim, M. Sars, Nyt Magaz. Naturvid. 1851, Bd. vi. p. 178 



( Siphonudoitalium, 1858). 

 D. lohatum, G. }i. Sowerbv, Jun., Thes. Conch. (18G0), vol. iii. p. 



100, fig. 44. 



Body whiti.sh, gelatinous, and nearly transparent : ma)itle 

 rather thick, forming a collar round the foot : tentacles i\\x(ta.i)i- 

 like, very slender, and having oblong tij).s or bulbs ; they are 

 not numerous, but extensile and irregular in length, issuing 

 from underneath the edge of the mantle : foot cylindrical, ex- 

 tensile, 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 

 notchfd edges : crcrctal fold or tail at the narrowest end of 

 the shell, tubular, and having the front split open and exposed 



11* 



