PROSOBRANCHIATA. 287 
PLEUROTOMA DENTICULA. Nyst. 1843. Descr. des Coq., &e., de la Belg., p. 526, t. 44, 
fig. 2. 
— Bell. 1845. Monogr. Pleurot. foss. Piem. (Mem. R. Accad. Sc. 
di Torino, 2d ser., vol. ix, p. 576, t. 3, fig. 7). 
= — Rouault. 1848. Foss. du terr. Eocene des Env. de Pau (Mem. Soc. 
Géol. de France, 2d ser., vol. iii, p. 484, t. 16, fig. 22). 
— SUBCARINATA? Rowault. 1848. Ibid., t. 16, fig. 23. 
— PLEBEIA. Sow. 1850. Dixon’s Geol., &c., of Sussex, p. 184, t. 6, fig. 23. 
-- — Morris. 1854. Catal. Brit. Foss., p. 270. 
— — Forbes. 1856. Mem. Geol. Surv. (Tert. fluv.-mar. form., &c.), 
p- 154, t. 5, fig. 1, a, 6 (excl. var. 6, fig. 2). 
P. testa fusiformi, turritd, concentrice lineata : spird elata, acuminata : anfractibus ad 
humeros carinatis, tuberculatis ; postice concavis, ad suturam lined elevatd, acutd, cinctis ; 
ultimo anfractu brevi, in canalem longiusculum, sub-rectum producto ; tuberculis transversim 
oblongis, medio sulcatis ; lineis concentricis supra canalem et margines posticas anfractuum 
Jiliformibus, sub-equalibus, supra medias partes elevatioribus, irregularibus: aperturd 
obovata ; labro drcuato, acuto, ad humerum sinuato ; sinu profundo, sub-trigono. 
Var. 1, tonaava (fig. 7d); testa minori, angustiori : marginibus posticis anfractuum 
tuberculisque exilissime lineatis ; tuberculis distantioribus, erassioribus. 
Var, 2, Macrosta (fig. 7 e); testd breviorr: ultimo anfractu tres vel quatuor lineas 
transversas eminentiores in medio gerentt. 
Var. 3, mutica; testd spird obtusiusculd; lineis concentricis ad interstitia inter 
lineas majores et supra margines exilissimis, confertis, regularibus, equalibus ; tuberculis 
minoribus, ultimo anfractu sepe obsoletis. 
Var. 4, GRACILENTA (fig. 7/); testd minori, graciliori: lineis concentricis elevatis, 
acutis, regularibus. 
Var. 5, conuuus (fig. 79); testd graciliori: spird elatiori, sub-conicd : marginibus 
posticis anfractuum paullo declivis, vie cavatis; tuberculis minoribus, compressis, denti- 
FSormibus ; lineis concentricis per lineas tncrementi sub-decussatis, postice numerosioribus, 
regularibus, ceterum distantibus : canali antico breviort. 
Var. 6, ODONTELLA (fig. 7 2); testd minor’, graciliori: lineis concentricis supra 
margines anfractuum exilissimis ; tuberculis mininis, sub-dentiformibus, 
Shell fusiform, turreted, pointed, spirally lined, tuberculated: the spire, formed 
of eight or nine volutions, exclusive of a longitudinally ribbed conical pullus, is much 
produced, being nearly double the length of the aperture. The whorls are flatly 
convex at the sides, and rather broadly carinated at the shoulders, round which they 
present a series of transversely oblong tubercles, which are furrowed across the middle, 
and sometimes become obsolete on the last whorl ; the posterior margins are narrow, 
concave, and bordered round the suture by a very prominent, sharp, ridge-like line ; 
and one or two fine concentric lines traverse the hollow of the margins. The concentric 
lines over the anterior canal are rather close-set, thread-like, and nearly equal ; over 
