PROSOBRANCHIATA. 321 
PLEUROTOMA CLAVICULARTS. Desh. 1832. Encyclop. Mécthod. (Vers.), vol. iii, p. 796, 
No. 12. 
— — Desh. 1824-37. Coq. foss., &c., de Paris, vol. ii, p. 437, t. 69, 
f. 9, 10, and 15-18. 
— prisca. Desh. 1824-37. Idem, vol. ii, p. 436, t. 69, f. 1, 2. 
— CLAVICULARE. Phil. 1846. Tert. foss. Magdeburg, p. 63, No. 113. 
— cLAVicuLARIS. Bronn, 1848. Index Palzontol., p. 1002. 
— Prisca. Bronn, 1848. Idem, p. 1008. 
— CLAVICULARIS. Rouwault, 1848. Foss. du térr. éoc., &c., de Pau (Mém. Soe. 
Geol. de France, 2d ser., vol. iii, p. 481), No. 83. 
— Prisca. Sow. 1850. Dixon’s Geol., &c., of Sussex, p. 102, t. 7, fig. 24; 
and p. 119, t. 14, fig. 30. 
— — Bell. 1851. Foss. Nummul. du Comté de Nice (Mém. Soc. Geol. 
de France, 2d ser., vol. iv, p. 222), No. 86. 
— CLAVIcULARIS. Bell. 1851. Idem, No. 87. 
—_— — D’ Orb. 1852. Prod. de Paléontol., vol. iil, p. 359; 25° Ktage ; 
Parisien, A, No. 404. 
_— Prisca. D’Ord. 1852. Idem, vol. iii, p. 416; 25° Etage; Parisien, B, No. 
1475. 
— cLavicuLaris. Wyst. 1836. Coq. foss. de Hoesselt, &c., p. 31, No. 79. 
P. testa elongato-fusiformi, sub-glabrd : spird elatd, sub-conicd, acuminata : anfractibus 
ventricosis, postice lineato-marginatis, ad basin transversim sulcatis, ceterum levibus ; ultimo 
anfractu in canali lato, indistincto, exeunte, ad extremitatem sub-profunde emarginato : 
apertura oblongo-ovali ; labro aliformi, tenui, acuto; sinu lato, breviusculo, sub-trigono, 
anticam in marginem collocato ; labio antice incrassato, reflexo ; columella leviter contorta, 
antice cristata. 
Shell elongated, fusiform, nearly smooth; the spire almost conical, pointed, and 
moderately elevated, being of equal length with the aperture. The whorls are slightly 
ventricose; when young, the whole surface is covered with moderately distant, 
concentric, raised lines, in which state it resembles P. ji/osa (Lamk.) ; these lines, how- 
ever, are lost on the fourth or fifth volution, and the whorls afterwards become 
smooth and shining, except at the base and over the posterior margins, round the 
sutural edges of which last run three or four fine threadlike, raised lines, occasionally 
replaced by two or three shallow, obscure furrows ; the last whorl is nearly conical, 
obscurely sulcated at the base and deeply notched at the extremity ; the anterior canal 
is wide, very short, and indistinct. The aperture is narrow and of an oblong-oval form ; 
the outer lip wing-shaped, projecting towards the front, thin and sharp on the edge, and 
smooth within ; the sinus, which is in the very front of the margin, is wide, moderately 
deep, somewhat triangular in form, and widely rounded at the extremity ; the inner 
lip is much thickened, and is produced and bent outwards in front, giving an umbilicated 
appearance to the columella, which is slightly twisted and prominently crested to- 
wards the base. ‘ 
It appears to me to be impossible, satisfactorily, to separate P. clavicularis from 
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