PROSOBRANCHIATA. 329 
raised lines, so faint as to be scarcely visible to the naked eye; the longitudinal ribs 
also are thicker and more distant, and they extend to the very front of the whorl. 
Size.—Axis, rather more than 6-12ths of an inch; diameter, rather more than 
2-12ths of an inch. 
Localities.—Headon Hill, and Colwell Bay, Isle of Wight; and Hordwell. 
No. 251. Borsonza semicostata. J. L. Edwards. Tab. XXXIII, fig. 13, a, 6. 
B. testé ovato-fusiformi, semi-costatd, omnino.spiraliter lineata: spird elatd, turrité . 
anfractibus convewiusculis, postice canaliculatis ; costis numerosis, rotundatis ; lineis spi- 
ralibus elevatis, acutis, supra margines .anfractium evilibus, regularibus ; ceterim irregu- 
laribus, sub-distantibus, duabus sub-mediunis elatioribus : apertura oblongo-ovali, in canalen 
latum perbrevem productd ; labro leviter arcuato, postice sinuato, intus levi; columella 
oblique inequaliter biplicatd, plicd antica nunori. 
Shell small, ovately fusiform, longitudinally ribbed, and covered with raised, con- 
centric lines ; the spire turreted and elevated, exceeding the aperture in length. The 
whorls, which are six in number without the pullus, are convex, and channelled round 
the posterior margins ; the last whorl is rather suddenly contracted towards the front. 
tapering thence gradually towards the base, where it terminates in a very short, wide 
canal. The ribs are rather numerous, not very broad, rounded on the upper surface, 
of equal thickness, and short, ending abruptly where the whorl contracts ; the trans- 
verse lines over the posterior margins are very fine, even, and regular; a sharp, 
elevated line crosses the shoulders, in front of which appear four other elevated lines, 
which gradually become more and more prominent and distant as they recede from 
the shoulders; the front two are more prominent and wider apart than the rest ; they 
are separated by a broad, concave furrow, and swelled into small, tooth-like knobs, 
where they cross the longitudinal ribs; the lines over the front part of the whorl and 
the canal are irregular and very obscure, almost obsolete. The aperture is of an 
oblong-oval shape; the outer lip is very slightly arched, and presents a shallow and 
not very wide, rounded sinus, placed in the marginal depression; the columella 
is nearly straight, and furnished with two unequal, oblique folds, placed near the 
middle, the front one of which is the smaller. 
In general aspect, this shell so closely resembles Lorsonza sulcata, that a doubt 
may fairly be raised whether it ought not to be regarded as.a variety of that species. 
It will be seen, however, on comparison, that in B. swlcata the spire is longer, that 
the posterior margins are not so wide nor so deeply channelled, and that they are 
spirally lined, and not smooth; that the cost are narrower and more numerous, and 
the transverse ornamentation quite distinct in character; that the outer lip is not so 
42 
