256 EOCENE MOLLUSCA. 
whorl, and are much shortened on the earlier whorls, assuming the appearance of 
oblong tubercles ; and the decussation by the concentric lines disappears. 
The present species presents a close analogy with P. scabriuscula, with which 
it may, especially in the young state, be readily confounded. On comparing adult 
shells, however, it will be found that, in this species, the shell is wider, the spire 
more pointed, the whorls less bluntly angulated at the shoulders, and more 
depressed and more deeply channeled round the margin, giving a decidedly turreted 
character to the spire; the whorls themselves are more numerous and _ shorter, 
and, in the typical form, the sharp ribs and prominent concentric lines give a rougher 
aspect to the surface. In the varieties a somewhat closer approximation will be 
found in the ornamentation of the two species; but, in other respects, the charac- 
teristic distinctions are preserved. 
From P. constricta, the only other species with which it might be confounded, 
it is separated by the depressed margins, and more sharply angulated shoulders 
of the whorls, the more regular costellation, and the deep, narrow sinus of that species. 
Size.—Axis, rather more than 8-12ths of an inch; diameter, 3-12ths of an inch. 
Localities. —Barton, Highcliff; not common. 
No. 178. Pievroroma constricta. F. EF. Edwards. Tab. XXIX, fig. 1, a—e. 
P. testé elongato-fusiformi, longitudinaliter costellatd, concentrice lineata: spird 
conoided, sub-acuminatd, aperturam in longitudine paullo superanti: anfractibus depresso- 
convewis, ultimo anfractu in canali brevi, terminanti ; marginibus posticis leviter declivis, 
canaliculatis, plicatis, ad suturam marginatis ; costellis crebris, angustis, obliquis ; lineis 
concentricis, acutis, denticulatis: apertura oblongo-ovali; labro leviter arcuato; sinu 
angusto, profundo, trigono, anticd in margine collocato. 
Shell elongated, fusiform, longitudinally ribbed, and concentrically lined; the 
spire, formed of seven or eight whorls, is rather conical, pointed, and moderately 
elevated, barely exceeding the body-whorl in length; whorls flatly convex; the 
posterior margins widely and deeply channeled, thickened at the sutural edges, and 
bordered by a single sharp, prominently raised line; the surface of the marginal 
furrow presents a series of prominent, curved plications, formed by the successive 
margins of the advancing sinus. The longitudinal ribs are numerous, slender, 
oblique, slightly curved, and extend almost to the very front of the whorl; the 
concentric lines are sharp, prominent, more or less distant in different individuals, 
and denticulated at the points where they cross the ribs. The aperture is of an 
oblong-oval form, and terminates in front in a short, moderately wide, canal; the 
outer lip is but slightly arched, thin, sharp-edged, and smooth within; the sinus 
is trigonal, narrow, very deep, and placed in the front part of the margin. 
