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. ¢eztiliosa 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moyens, at Senlis, at present unpublished, but which M. Deshayes purposes to 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, 15 inch; diameter, not quite half an inch. 
Locality — Bramshaw. 
No. 15]. PreuRoTOMA LANCEOLATA, Ff. £. Edwards. Tab. XXVI, fig. 11 a, 6. 
P. testé elongata, angustd, fusiformi, spiraliter lineatd : spird elevatd, sub-conied, tuber- 
culatad: anfractibus convexiusculis ; marginibus posticis mediocriter latis, pauxillum 
declivis, vie cavatis, transversim exilissime lineatis; ultimo anfractu antice gradatim 
attenuato, in canali longo exeunti: apertura lanceolata ; labro valde arcuato ; sinu lato 
sub-trigono, in margine collocato. . 
Shell long, very narrow, fusiform, ornamented with spiral, raised lines: the oar 
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 
