160 NEW-YORK FAUNA MOLLUSCA. 



SECTION 7. CIRROBRANCHIA. 



Animal with its foot anterior and terminal, elongated into a conical shape, in order to penetrate 

 sand. Gills in the form of numerous long filaments, arising from two radical lobes above 

 the neck, and enveloped by the mantle, which opens in front : afeio tentacular expansions. 

 Eyes — — . Sexes united. Shell simple, symmetrical, tubular. 



FAMILY DENTALID^E. 



With the characters of the section. Only one family as yet observed. 



GENUS DENTALIUM. Linneus. 



Animal with small oval distinct head. Mouth terminal, surrounded by digitated labial pro- 

 cesses, furnished with a pair of lateral oval jaws bristled with points. The cylindrical 

 mantle enveloping nearly the anterior half, terminating in front in a sort of collar, through 

 which is apparent the circular opening of the foot. Foot ending in front in a sort of cup, 

 in the centre of which is a conical appendix. Gills disposed in long filaments, arranged in 

 two groups on each side of the upper part of the neck. Vent median, at the posterior ex- 

 tremity. Generative organs unknown. Shell tubular, elongated, conical, not spiral, very 

 slightly curved, open at both ends. 



Obs. Nearly fifty fossil and recent species of this genus are noticed in the most recent 

 systematic works, of which one fossil species only is noticed from the United States. In the 

 most recent edition of Lamarck's Animaux sans vertebres, the animals of this genus are still 

 arranged among the Annelides. But one recent species has been observed on our coast. 



Dentalium DENTALIS. 



PLATE X. FIG 197. 



Dentalium dentalis. Lin. Syst. Nat. 1263. 



D. id. Gould, Invertebrata of Mass. p. 15C, fig. 5. excl. syn. 



Description. " Shell slender and tapering, shaped like an elephant's tusk ; the tip cut off, 

 leaving a very small opening. Surface rather glossy, yellowish white, marked with about 

 twenty closely arranged unequal rib-like stria?, running the whole length of the shell. Length 

 about an inch ; diameter at the larger end about one-eighth of an inch." 



Two specimens of this shell, according to Dr. Gould, whose description I have copied, 

 were obtained from the stomachs of codfish on the coast of Massachusetts. 



