BULLA Linn. &c, 
Gen. Char. An ovato-globose* convoluted 
univalved shell ; columella none ; spire not 
produced ; aperture as long as as the shell ; 
its external margin sharp. 
In general form the shells of this Genus vary from cy- 
lindrical to obovate ; they are usually thin, sometimes 
almost membranaceous, and fragile; the want of a colu- 
mella, and the thin edge of the aperture distinguish the 
species of this Genus as it is now defined by Lamarck, 
from several that were associated with them by Linneus, 
such as the Ovulse, &c. and also from the Volvariae. In 
some species there is a thickening of the inner lip of the 
aperture that much resembles a columella, but this is 
never plaited ; and such as have it may perhaps hereafter 
form a distinct Genus. 
The animal to which the shell is attached, is remark- 
able for having no antennaB, and for the foot being 
laterally expanded so as to be used in the way of fins to 
swim with ; the mantle does not include the shell. 
BULLA convoluta. 
TAB. CCCCLX1 1. 
Spec, Char. Very cylindrical, smooth ; aper- 
ture linear, expanded a little way from the 
base; vertex obtuse, perforated. 
Syn. Bulla convoluta Brocchi , p. 277. tab. 1. 
.fig- 7. 
JLength two and a half times the width ; the superior 
extremity is broad, or rather the upper part of the whorls 
is, as it were truncated, the spire being sunk deeply into 
its centre. 
Found in Crag, by the Rev. G. R. Leathes. It does 
not appear to be so strictly cylindrical as required by the 
description given by Brocchi, but agrees well with his s 
figure. 
