64 GASTEROPODA. ANCYLUS. 
Genus 1. — BULLA. — Linneus. 
Generic Character.— Shell convolute, oval, with a 
depression above in place of a spire ; aperture longitudinal, 
as long, or longer than the convolutions, straitened above, 
and expanded beneath, where it is effuse ; outer lip thin; 
columellar lip generally reflected with a coating of shelly 
matter. 
Bulla attenuata. Plate IV. fig. 11. 
The Bulle are marine shells common to tropical climates, as well as to 
almost all countries. Several inhabit the British seas. 
Sowerby has united the Bulla and Bull@a of Lamarck, in which we have 
followed him, = 
The fossil Bulle are found in the Tertiary formation, and in the Green 
Sand. 
Genus II. — UTRICULUS. — Brown. 
Generic Character. — Shell small, oblong-ovate; body 
very large, spire very short, with rounded volutions ; aper- 
ture as long as the body, narrow above, wide, and rounded 
at the base ; outer lip thin, and slightly inflected ; inner lip 
not reflected on the columella. 
Utriculus glaber. Plate V. fig. 9. 
The shells of this genus are marine, the recent type of the genus is the Bulla 
yetusa of Montagu. Fossil species occur in the Oolite, at Cloughton and 
Brandsby, and in the inferior Oolite, at Cloughton. 
The shell we have figured is the Acteon glaber of Phillips, but it is inadmis- 
sible into that genus, being destitute of a fold on the columella. 
TRIBE IJ.—CALYPTRACEA. 
The branchie of the animal situated in a dorsal cavity near 
the neck, and included in the cavity, or projecting beyond its 
shell, which is invariably exterior. 
Genus IIIl. — ANCYLUS. — Miller. 
Generic Character. — Shell thin, obliquely conical, pa- 
telliform ; vertex somewhat pointed, short, turned back- 
wards, and slightly inwards, but not spiral ; aperture oval, 
or oblong, with the margins simple and entire. 
Ancylus elegans. Plate IV. fig. 14. 
‘Two recent species of this genus inhabit the fresh waters of Europe, and 
both are natives of Britain. They differ from the Patelle in the apex being 
turned backwards. 
Fossil species occur in the Calcaire-grossier. 
