PROSOBRANCHIATA. 223 



The present species is an intermediate form between P. crassicosta and P. dentata ; 

 but the thick, rounded, distant ribs, the crowded transverse ornamentation, and 

 the broader and shorter canal, render it easily distinguishable. 



Size. — Axis, 1 inch and 5-12ths nearly (35 millem.) ; diameter, half an inch (13 

 millem.). The French shells attained a somewhat larger size. 



Localities. — Bracklesham Bay; Bramshaw. French — Monneville (fide Desk.), 

 Aumont, Acy-en-Mulcien (fide D"Orb.). It is very rare in England, but, apparently, 

 common in the French beds. 



No. 148. Pleurotoma exorta, Solander. Tab. XXVI, fig. 12 a, b. 



Murex exortus, Sol. 1766. Brand., Foss. Hanton., p. 20, fig. 32. 

 Pleurotoma exorta, Sow. 1816. Min. Conchol., vol. ii, p. 104, t. 146, fig. 2. 

 _ _ Morris. 1843. Cat. Brit. Foss., p. 157. 



— — Sow. 1850. Dixon's Geol., &c, of Sussex, p. 102. 



— — VOrb. 1850. Prod, de PalSont., vol. ii, p. 359, No. 408. 



Nee Pleurotoma exorta, Nyst. 1835. Recher. sur les coq. foss., &c., d'Anvers, p. 28, No. 27. 

 nee — — De Kon. 1837. Descr. des coq. foss., &c., de Basele, Boom, &c., p. 22, 



No. 21. 

 nee — — D'Orb. 1850. Prod, de Paleont., vol. iii, p. 13, No. 195 m. 



P. testa elongato-fusiformi, turritd, undique spiraliter lineatd: spird elevatd, sub- 

 conicd, nodulosd ; anfractibus convexis, prioribus obscure costellatis ; ultimo anfractu sub- 

 conico scilicet sensim attenuato, in canali longiusculo exeunti ; marginibus posticis declivis, 

 cavatis, ad suturam incrassatis, transversim exilissime lineatis ; striis spiralibus nonnullis 

 remotiusculis, eminenlioribus, acutis ; cceteris sublilissimis aqualibus : aperturd lanceolatd ; 

 labro valde arcuato, tenui ; sinu lato, in margine collocato. 



Shell elongated, fusiform, turreted, ornamented with spiral raised lines ; the spire 

 elevated and terminating in a small pointed pullus formed of two or three smooth 

 volutions : whorls convex, the earlier ones very broadly and obscurely ribbed, giving a 

 nodulous aspect to the spire ; the posterior margins are somewhat thickened on the 

 sutural edge, and but slightly depressed, so that the spire presents a nearly conical form ; 

 the space between the suture and the shoulder is channeled and covered with very 

 fine and regular concentric lines, so slender as scarcely to be visible by the naked eye 

 or to detract from the smoothness of the surface. On the middle and front parts of 

 the whorls, some of the spiral lines, rather distant from each other, are sharp and 

 elevated ; the rest, which cover the intermediate spaces, are very fine, close-set, 

 and regular, although somewhat unequally prominent. The aperture is lanceolate, 

 and terminates in a moderately long canal, gradually diminishing in width, and thus 



