20 CRETACEOUS GASTROPODA 
angusta atque elongata, mterne levissima, marginibus conjunctis, callosissimis, partem 
ventralem teste omnino tegentibus ; labro antice valde insinuato, posterius lobato : lobo 
hamiformi, crasso, contorto, lateraliter compresso, acute terminanti, supra infraque 
canaliculato ; labio crassissimo, callum ovalem elevatum formante ; rostro callose- 
marginato, lato, interne canaliculato, intorto, supra sceepius incrustato seu prope muar- 
gimem exteriorem subcanaliculato. 
The general form of the shell is elliptical, somewhat elongated in the direction 
of the axis. There are usually six whorls present, forming a spire with an angle 
varying from 60 to 65 degrees; they are convex, the uppermost very distinctly and 
densely striated in a spiral direction ; these striz become afterwards nearly obsolete. 
On the penultimate whorl slight transversal costs appear, which on the last whorl are 
flexuous, partly and gradually disappearing towards the anterior canal, while others 
placed nearer to the outer margin do the same, or terminate in more or less 
elevated turbercles, corresponding with the hook-like prolongation of the outer lip. 
On perfect specimens, the majority of which measure about 30 mm., the last whorl 
occupies usually a little more than three-fourths of the total height. The aperture is 
elongated-eliptical, being internally much narrowed by the callosity, which thickens 
and unites both margins. Some of our specimens exhibit on the callose mass round 
the aperture a kind of purple colouring, which partly seems to be original, resem- 
bling that of several living Srromarpm. On the posterior part of the outer lips, 
between one-fourth and one-half the distance from the suture, the callose margin 
projects into a hook-like lobe, this being turned upwards, contorted towards the 
aperture, laterally more or less compressed, often so much as to form a sharp ridge 
on the ventral side; internally and externally it is canaliculated by slight furrows, 
which, however, often quite disappear under the coverings of the thickened lip. Near 
the anterior extremity the outer peristome is very deeply insinuated. The canal is 
slender in proportion to the last whorl; it is bounded like the outer peristome all 
round with a thick margin, curving inward at the same time; the internal furrow, 
which seems to have been produced by the elongated sipho, remains always dis- 
tinct up to the termination, while the exterior one, which marks the place where 
the two thickened margins join, becomes often obliterated under the numerous 
layers of the callosity. The inner lip is exceedingly thick and forms on the ventral 
side an oval large mass of enamel-coating, the last or newest layers of this mass 
extend sometimes over the entire surface of the shell, with the exception of a small 
upper dorso-lateral portion. 
There is not much variation in the form of the shell of this species, except that 
the last whorl is sometimes more, sometimes less inflated or gibbose. The hook-like 
lobe of the outer lip is occasionally less contorted, but somewhat more bent outside. 
The stronger or lesser development of the callosity causes all these differences and 
gives the shell often a totally different aspect. Specimens, on which the inner and 
outer callose mass has been lost, make quite the impression of being a Fusus or 
some allied genus. We have given figures of several of these forms and refer here 
to the explanations which accompany the plate (vide figs. 2—5). 
