BULLIDA. 359 
narrow behind, widened in front; columella with two folds. C. 
bidentatus, ’Orb. (Ixxxvii, 33), Tertiary ; West Indies: 
voLvu“ta, A. Adams. Shell subeylindrical, attenuated to a 
point posteriorly, to which the narrow aperture extends ; spire 
concealed ; outer lip sharp; columella with an obsolete anterior 
plication. C. acuminata, Brug, Axxxvii, 34). 
ACTHONELLA, @Orb. (€Volvulina, Stolicz.) Shell convolute, 
like Volvula, attenuated at both ends, aperture linear, inner lip 
anteriorly thickened and provided with three folds. The shells, 
which are as yet only known from cretaceous deposits, mostly 
closely resemble the recent Volvula, differing from it merely by 
the presence of three columellar folds on the anterior portion of 
the inner lip. C. crassa, d’Orb. (1xxxviii, 61). ‘Cretaceous. 
» Urricutus, Brown. 
‘Distr.—Northern ‘Several'sp: -UvCecillei; Phil. (Ixxxvii, 32). 
‘Shell subcylindrical,; with short spire, and. thin epidermis ; 
aperture narrow behind, wider in front; columella not plicated ; 
outer lip thin. 
’ Utrieulus is regarded as a distinct genus by Jeffreys, differing 
from Cylichna by the tentacles being separate, the eyes distinct, 
the gizzard horny, and the: shell having a visible spire with a 
eae ae apex. 
DrapHana, Brown. 
6532505 titphisph pea! Lovén, ) 
Distr.—A fewsp. Northern,U.8., Europe. D. debilis, Gould 
(Ixxxvii, 35). 
Shell thin, transparent, oval-globular; spire very short; aper- 
ture much widened anteriorly ; columella a little sinuous ; outer 
Jip thin, sinuous, broadly rounded anteriorly. 
Head-disk broad and_ short; tentacular lobes short, conical, 
lateral, wide apart ; eyes immersed in their hind bases. Mantle- 
margin slightly thickened. Foot short, bilobed behind. 
In this genus, as in Rissoella, Gray, the eyes are placed far 
back behind the head, so that in order to render the vision of 
the animal distinct, the shell is nearly transparent. . The head of 
the animal is very short, and the tentacles wide and far apart. 
Famity BULLID&. 
Shell spiral, ventricose, rather thick; maeulated and banded 
in the typical genus, white in others; spire involute; external, 
but usually partly covered by the lateral lobes of the foot. 
Bucia, Linn. 
Baste —50 sp. Universal. B.-ampulla, Linn. (Ixxxvii, 36). 
Fossil. Cretaceous—, 
Shell oval-globular, smooth, spotted, marbled or zoned ; spire 
