M. Deshayes' Monograph of Dentalium. 179 



animal kingdom. It must, however, be admitted that the almost perfect 

 symmetry of its organs by no means accords with the irregularity univer- 

 sally exhibited by those of the MoUusca, not one of which even approxi- 

 mates to it in this respect. For the present, at least, and until further 

 and more complete dissections, especially of the larger species, found in 

 the Indian seas, shall have thoroughly developed its organisation, its pre- 

 cise situation must be regarded as doubtful. 



Dentalium. 



Animal. Body elongated, conical, truncate anteriorly, inclosed in 

 a mantle which is terminated in front by a sphincter-like, fringed or 

 plaited, incrassation. Foot anterior, proboscidiform, terminated in front 

 by a conical appendix received into a kind of calyx with festooned margins. 

 Head distinct, pedicelled. Lips furnished with tentacula. Eyes or eye- 

 bearing tentacula none. Branchice cirrhous, in two cervical symmetrical 

 bundles. Jaws two, horny, lateral, oval, cleft. Anus terminal, median, 

 in a kind of funnel-shaped enlargement at the posterior extremity, capable 

 of protrusion from the shell. Organs of generation unknown. 



Shell, regular, conical, elongated, symmetrical, more or less 

 curved; concavity ventral, convexity dorsal; open at the two extremi- 

 ties; anterior opening larger, simple, usually oblique ; the posterior one 

 smaller, sometimes lengthened by a slit which is generally median and 

 dorsal. 



Obs. In the succeeding descriptions, M. Deshayes supposes the 

 shell under examination to be placed with its larger extremity or bcise 

 in front, its small extremity or apex posteriorly, its concave or ventral 

 surface downwards, and its convex or dorsal surface upwards ; the large 

 opening of the shell which occupies its base thus becoming anterior, and 

 the smaller one of the apex posterior, and the shell presenting four 

 surfaces, an inferior or ventral, a superior or dorsal, and two lateral, 

 one right and the other left. 



The D. corneum, Linn., the D. pellucidum, Linn., and the D. nigrum, 

 Lam., are rejected from the genus as the cases of the larvse of Phry- 

 gane<2; as are also the D. Radicula, Lam., and the D. deforme, Lam., 

 which are evidently Serpulce. 



