78 EOCENE MOLLUSCA. 
No. 27. Pupa oryza. JF. 2. Edwards. Tab. XIV, fig. 3a—d. 
P. testa pared, ovato-cylindraced, ad utramque extremitatem equalter attenuata ; apice 
sub-obtuso; anfractibus octonis, convewiusculis, longitudinaliter tenuissime costellatis ; suturis 
profundis ; apertura ovato-oblongd, angustd, obliqua, quaternis dentibus magnis tnstructa. 
A small cylindrical oval shell, tapering equally towards both extremities ; the apex 
is rather blunt; the whorls, which are eight in number, are slightly convex, separated 
by a deep conspicuous suture, and transversely costellated ; the costellz are numerous, 
very slender, and oblique. The aperture is ovate-oblong, narrow, and somewhat 
oblique; the outer lip is furnished with four prominent lamelliform teeth, of which 
the two anterior are the longest. 
I possess only one specimen, a cast, of this species; and the state of the aperture 
does not enable me to say whether the columellar lip is furnished with teeth. The 
species appears to be perfectly distinct. 
Size.— Axis 2 lines; diameter 1 line. 
Locality—Headon Hill. 
Genus 10th. Cuausiu1a.* Draparnaud. 1805. 
Gen. Chav.—Shell sinistral, cylindrical, elongated, consisting of numerous volutions, 
generally transversely striated; rather blunt at the apex, and enlarged towards the 
middle; aperture irregular, oval; peristome continuous, free, reflected, with several 
columellar and other tooth-like plaits, and furnished with an appendage, termed the 
clausium, attached to the columella, by which the aperture is partially closed when the 
animal is withdrawn into the shell. 
The clausium, from which the present genus derives its name, answers the purpose 
of an operculum, with which, however, it presents no further analogy than that it 
serves to enclose and protect the animal within the shell. It consists of a narrow, flat, 
and very thin calcareous pedicle attached by the posterior extremity to the columella, 
and expanding at the opposite end into a linguiform plate, which nearly closes the 
aperture of the penultimate whorl, a small canal across the anterior part of the aperture 
being left uncovered, probably for the purpose of respiration. In some species when 
the outer lip presents teeth, the clausium is notched for their reception. This curious 
appendage is formed when the animal approaches maturity, probably at the same time 
with the projected reflected mouth. The pedicle is very flexible, and yields to the 
* Etym. Clausium, (quasi clausus, closed, or claustrum, a door,) the appendage by means of which the 
animal is enclosed in the shell. 
