100 DENTALIUM. 



standing error of applying Linnseus's name of eburneum to this 

 species, and that of politwm to the shell to which Linnasus evi- 

 dently meant to apply the name eburneum. T. politum is distin- 

 guished from all other species by the incised lines which divide its 

 whole length into oblique rings. It is excessively rare in a recent 

 state, but well known among the fossils of the Paris basin. The 

 figure is from Mr. Hanley's recent specimen. 



20. D. lobatum, Sowlt. Thes., f. 44. — Testa subhyalina, valide 

 arcuata, curta, lsevi, alba, seu partim pallide fulva ; apice obtuso, 

 truncate, in lobis quatuor diviso. — This curious shell is smooth, 

 short, and strongly curved in proportion to its length. The apex 

 is divided into four lobes, the dorsal and ventral ones being each 

 slightly subdivided. This peculiarity may possibly indicate an 

 important difference in the animal structure, and until that is 

 known, we cannot be certain even of its generic position. 



21. D. Tarentinum, land:, f. 19, 20, 49.— Testa solida, va- 

 lide arcuata, lata, alba, nonnunquam roseo-tincta, versus apicem 

 longitudinaliter striata ; apice acuminate, plerumque integro. — 

 Unless much worn, specimens of this shell always show strise near 

 the apex, which, with the less cylindrical forms, distinguish them 

 from D. entale. The two species have, by some authors, been even 

 generically separated, on account of the absence of apical notch 

 in D. Tarentinum. In a numerous series of both species now 

 before us, however, we meet with cases where the notch is want- 

 ing in the former and quite traceable in the latter. 



22. D. aculeatum, Sowb., f. 63. — Testa alba, valide arcuata, 

 ina3qualiter striata; apice attenuata, acuminata, integra. — Not un- 

 like the very young of J). Tarentinum, but more acuminated, and 

 with unequal instead of equal strife. 



28. D. curtum, ?, f. 64. — Testa subviridi, subcylindracea, 

 tenue striata, brevi; apice obtuso, vix fissurato. — A small, cylin- 

 drical, pale-greenish shell, with obtuse apex and fine stria;. 



24. D. semipolitum, Sowb. Ser., f. 23. — Testa subhyalina, te- 

 nui, alba, angusta, versus apicem roseo-tincta, tenuissime striata, 

 deinde polita ; apice nonnunquam antice aut lateraliter fissurato. — 

 Minutely striated at the narrow end, and quite polished from the 

 centre to the margin. More glassy and thin than B. Tarentinum. 



25. D. Lessoni, Desk., f. 15, 16, 17, IS.— Testa elongata, 

 leviter arcuata, pallide fulva seu flavida, nonnunquam roseo-tincta, 

 prope apicem 12-costata, deinde costis minoribus interstriata, prope 

 marginein polita; apice integro. — Bather variable, more or less 



