PROSOBRANCHIATA. 257 
The present species much resembles P. innewa, with which, in fact, at first sight, 
it may be easily confounded; on a closer inspection, however, differences will be 
detected which render it impossible to regard it as even a strongly-marked 
variety of P. inneva. In the general form, P. constricta is a slenderer shell, with a 
more pointed spire, and, instead of the shallow, obscure furrow, bordered by a row 
of granulations which runs round the posterior margins of the whorls in P. iznera, 
the present species presents a wide, conspicuous channel, defined by a sharp, elevated 
ridge; the outer lip is much less arched, and is not thickened or plicated within, 
and the sinus is deep, narrow, three-cornered, and placed in the front part of the 
margin, instead of the wide, rounded sinus extending over the whole width of the 
margin which characterises P. innewa. 
Size.—Axis, rather more than 8-12ths of an inch; diameter, 3-12ths of an inch. 
Localities —Barton, Highcliff, Highgate. 
No. 179. Preurotoma pyroota. F. &. Edwards. Tab. XXVIII, fig. 16, a—c. 
P. testi sub-fusiformi, turritd, longitudinaliter obscure costulatd, concentrice sulcata : 
anfractibus ad humeros carinatis, antice planulatis, sub-conicis, postice canaliculatis, 
transversim lineatis, crenato-marginatis ; costellis antice bifurcatis, sub-obsoletis: apertura 
oblongo-ovalt, in canali brevi exeunti ; labro intis plicifero ; sinu lato, sub-semicirculari, in 
margine collocato. 
Var. a. Testaé costellis distinctioribus, productioribus: anfractibus antice granoso- 
lineatis, cetertim levibus. 
Shell sub-fusiform, turreted, longitudinally ribbed, and concentrically furrowed : 
the spire, which consists of seven or eight volutions, exclusive of the smooth, conical 
pullus, is moderately elevated, forming about one half of the entire shell ; the whorls 
flat-sided, giving a nearly conical aspect to the anterior part of the shell, sharply 
carinated at the shoulders, and having the posterior margins channelled and bordered 
round the suture by a sharp, elevated line, simple or feebly crenulated, the concave 
space between which and the shoulder is smooth; the keel on the shoulders is 
notched with much regularity, presenting a row of oblong, somewhat oblique, rib-like 
tubercles. These tubercles are prolonged anteriorly, and bifurcate, forming two 
curved, narrow, obscure ribs, which are lost as they cross the middle of the whorls ; 
the concentric furrows are shallow and wide, the intervening spaces becoming 
gradually more elevated and sharper as they approach the base of the shell. The 
aperture is of a narrow, elongated, oval form, and terminates in front in a short, wide 
canal; the outer lip is slightly arched, somewhat thickened and plicated within ; 
and the sinus, which extends over the whole margin, is wide and deep, and nearly 
semicircular. 
33 
