226 EOCENE MOLLUSCA. 



lated at the shoulder ; the posterior margins rather wide, hollowed out, and thickened 

 on the sutural edge, which is bordered by two or three prominent, raised lines ; the 

 remaining surface of the margin is covered with very fine, close-set, concentric lines ; 

 the last whorl is small, and terminates in a wide and long canal, a little curved 

 near the anterior extremity. The ribs are distant, rounded, short, not extending to 

 the middle of the whorl, prolonged over the posterior margins almost to the suture, 

 and bearing at the shoulders of the whorls a row of transverse tooth-shaped tubercles. 

 The spiral lines over the middle and front parts of the whorls are numerous and 

 unequal ; some, at nearly regular and not very distant intervals, are rather thick and 

 prominent, and between these appear two or three slender, thread-like lines. The 

 aperture is ovate, the outer lip moderately arched, and the sinus, which is placed in 

 the middle of the margin, is wide but not deep. 



The P. crassi-costa bears a close resemblance to P. dentata, of which, perhaps, it 

 may prove to be merely a local variety. It presents, however, certain peculiarities of form 

 which appear to me sufficient to justify the separation. Thus the shell is narrower, 

 the spire relatively more produced ; the posterior margins of the whorls are not so 

 wide, the whorls themselves smaller and more suddenly contracted in front, and the 

 longitudinal ribs thicker and more distant. From P. textiliosa it is distinguishable by 

 the character of the transverse ornamentation, and the thick, rounded, and more 

 distant ribs of that species. It approaches very nearly to a species from the sables 

 moyens, at Senlis, at present unpublished, but which M. Deshayes purposes to 

 describe under the name P. Michelini, in his forthcoming appendix ; without a 

 comparison, however, with a better series of specimens of that species than I possess, 

 I do not venture to pronounce on the identity. Should the English and French shells 

 prove, eventually, to belong to the same species, the name proposed by M. Deshayes 

 will be entitled to priority. 



Size. — Axis, 1| inch ; diameter, not quite half an inch. 



Locality. — Bramshaw. 



No. 151. Pleurotoma lanceolata, F. K Edwards. Tab. XXVI, fig. 11 a, b. 



P. testa elongatd, angustd, fusiformi, spiraliter lineatd : spird elevatd, sub-conicd, tuber- 

 culoid : anfractibus convcxiusculis ; marginibus posticis mediocriter latis, pauxillum 

 declivis, vise cavatis, transversim exilissime lineatis ; ultimo anfractu antice gradatim 

 attenuato, in canali longo exeunli: aperturd lanceolata; labro valde arcuato ; sinu lato 

 mb-trigono, in margine collocato. 



Shell long, very narrow, fusiform, ornamented with spiral, raised lines : the spire 

 elevated, nearly conical, and terminating in a small, smooth, pointed pullus of two 

 volutions: the whorls, 9 — 11 in number, are but slightly convex, and in the young 



