﻿PROSOBRANCHIATA. 



287 



Pleurotoma denticula. Nyst. 1843. Descr. des Coq., &c, 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. 



Geol. de France, 2d ser., vol. iii, p. 484, t. 16, fig. 22). 



— scjb cabin ata 1 Rouault. 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, b (excl. var. b, fig. 2). 



P. testa fusiformi, turritd, concentrice lineatd : spird elatd, acuminata : anfractibus ad 

 humeros carinatis, tuberculatis ; postice concavis, ad suturam lined elevatd, acuta, cinctis ; 

 ultimo anfractu brevi, in canalem longiusculum, sub-rectum producto ; tuberculis transversim 

 oblongis, medio sulcatis ; lineis concentricis supra canalem et margines posticas anfractuum, 

 flliformibus, sub-cequalibus, supra medias partes elevatioribus, irregularibus •■ aperturd 

 obovatd ; labro drcuato, acuto, ad humerum sinuato ; sinu prof undo, sub-trigono. 



Var. 1, long^va (fig. 7d); testa minori, angustiori : marginibus posticis anfractuum 

 tuberculisque exilissime lineatis ; tuberculis distantioribus, crassioribus. 



Var. 2, macrobia (fig. 7 e); testa breviori: ultimo anfractu tres vel quatuor lineas 

 transversas eminentiores in medio gerenti. 



Var. 3, mutica ; testa spird obtusiusculd ; lineis concentricis ad interstitia inter 

 lineas majores et supra margines exilissimis, confertis, regularibus, aqualibus ; tuberculis 

 minoribus, ultimo anfractu sape obsoletis. 



Var. 4, gracilenta (fig. 7f)', testa minori, graciliori : lineis concentricis elevatis, 

 acutis, regularibus. 



Var. 5, conulus (fig. 7 g); testa graciliori: spird elatiori, sub-conicd : marginibus 

 posticis anfractuum paullo declivis, vix cavatis ; tuberculis minoribus, compressis, denti- 

 formibus ; lineis concentricis per lineas incrementi sub-decussatis, postice numerosioribus, 

 regularibus, caierum distantibus : canali antico breviori. 



Var. 6, odontella (fig. 7 h); testa minori, graciliori: lineis concentricis supra 

 margines anfractuum exilissimis ; tuberculis minimis, 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 



