GASTEROPODA. 



SOLENOCONCim 



DENTALIID^E. 



Genus DENTALIUM, Linn. 



Synon. — Tubulus, Dentale, Dentalis, Syringites, &c, wholly, or in part, of pre-Linmean authors. 



Dentalium, Linnaeus (1758*), Syst. Nat. (ed. X), 785.— Lamarck (1799), Prodr. Syst,, 78; and 

 (18011 Syst. An., 32R; also (1818) Hist., V, 341.— Blainv. et Defr. (1819), Diet. Sci. 

 Nat., XIII, 69.— Blainv. (1834), «7>., XXXII, 286; and (1825) Malac., 496.— Desh. (1825), 

 Monogr. in Mem. Soc. Nat. Hist, de Paris, II, 321 ; and (1830) Encyc. M€th., Ill, 65.— 

 Reeve (1841), Proceed. Zool. Soc, 73 ; and (1842) Conch. Syst., II, 5. — Forties and 

 Hanley (1853), Hist. Brit. Moll., II, 448— H. & A. Adams (1854), Genera Eecent Moll., 

 I, 458.— Gould & Binney (1870), Invert. Mass. (2d ed.), 266.— Tryon (1873), Am. 

 Marine Couch., 96 ; aud of numerous others. 



Ktym. — Dens, a tooth. 



Type. — Dentalium elephantinum, Linn. 



Shell slender, tubular, regularly tapering, and more or less arcuate from 

 the aperture to the posterior open end ; aperture simple, not constricted ; 

 posterior opening small, without a proper slit or denticulations, but some- 

 times with a faint dorsal (or dorsal and ventral) marginal indentation, and a 

 thin, slightly projecting, inner tube, ending in a dorso-ventral oval opening; 

 surface ornamented with longitudinal costse or striae. 



In this singular genus, the animal has a remarkably simple structure, 

 being without tentacles or eyes, or, indeed, even without a well-developed 

 head, and only a rudimentary foot. Yet it is known to have red blood. 



The genus Dentalium dates back to the Devonian epoch, and also ranges 

 through rocks, of all subsequent ages. It is also well represented in our 

 existing seas, where the recent species generally occur in deep waters, bur- 

 rowing in mud and sand. 



Dentalium gracilc, H & M. 



Plate 18, figs. 13, a, 6, c, d. 



Dentalium gracile, Hall aud Meek (1854), Mem. Am. Acad. Arts & Sci., Boston, V (n. s.), 393, pi, 3, tig. 11. 

 Dentalium fragile, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 69. 



Shell long, slender, gently curved from the apex to the larger extremity ; 

 section and aperture very nearly or quite circular; surface ornamented by 



* I am aware that the name Dentalium was used by Aldrovandus as far back as Hi 12. and by Lin- 

 naeus in 1T40 ; but as the binomial system only dates back to Liunaeus's tenth editiou, I do not go behind 

 its issue for the dates or authors of genera. 



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