404, CRETACEOUS GASTROPODA 
species, H. cytharella and prisca, which Deshayes describes from the Paris basin, 
are both transversally ribbed and have an elevated pointed spire, but otherwise 
they much resemble the next genus. Iam not acquainted with any other species 
belonging to this genus, and as its form is so extremely like many others belonging 
to the Prevrorourm., to the rusin= of the Wvurrcrps#, and also to the mzrrrwa, 
it is not advisable to form opinions from mere drawings, especially when the shells 
are not perfectly preserved for generic determination. 
12. Bullinula, Beck, 1840 (Bullina, Fér. apud H. and A. Adams, Gen. II, p. 8). 
Shell ovate, with a short spire, last whorl ventricose, embryonal whorls smooth 
and mammillated, rest of the surface spirally striated, outer lip thin, inner some- 
times partially covering the shell, columella thickened, often slightly hollowed 
out, occasionally somewhat twisted, anteriorly obliquely truncated, the outer lip 
being somewhat produced and effuse. 
The two oldest species apparently belonging to this genus are the jurassic 
Acteonina pulchella, VOrb., and Act. striato-suleata, Zittel and Goubert; they 
both differ from the recent Bullinula by having the columella more thickened. 
and solid. Strictly speaking, the difference is very slight, for in the recent species 
the columella is not distinctly hollowed out, but in consequence of the inner lip 
being so loosely attached to the previous whorl as not to cover every furrow on 
the shell a slight fissure is produced; it is, however, by no means distinctly traceable 
in all cases. There is no very distinct columellar fold as usually in Acteon, but 
some species like Bullinula scabra have the columella distinctly twisted anteriorly 
at the termination and also in the middle; thus they very closely approach Htalonia. 
I shall note a third fossil species from our cretaceous rocks, Bull. obtusiuscula, 
n. sp. I could also refer to the jurassic Acte@on Sedgwicki, Phil., and Act. pullus, 
M. and Lycett, or to the cretaceous Acteonina Icaunensis, Pictet and Camp., and 
a few tertiary species described in Deshayes’ last work, and others, but none of 
the existing figures are taken from such thoroughly perfect specimens as to make 
their generic determination sufficiently reliable. 
13.2? Kleinella, Adams, 1860 (Ann. mag. nat. hist., V, p. 302) has an ovate, 
thin, umbilicated shell, with the surface cancellated, aperture anteriorly produced, 
inner lip not plicated. The shell is said to resemble Acte@on, but is without a fold; 
from the reference to the form of the aperture and the thin outer lip and the 
hollow columella, I should think that the genus is closely allied to the previous 
one, if at all distinct from it. 
14. Aplustrum, Schumacher, 1817 (H. and A. Adams, Gen. IT, p. 6), differs 
from Bullinula by its smooth, somewhat thinner shell, more depressed spire, the 
columella being very thick, slightly twisted and truncated in front. The only 
species as yet known is d. aplustre, Linn., which, as Mr. G. Nevill tells me, 
is often found living on coral reefs at the South Coast of Ceylon, Mauritius, 
Bourbon, ete. No fossil species has as yet been noticed. 
15. Hydatina, Schumacher, 1817. Shell partially or wholly convolute, thin, 
ventricose, smooth or spirally sulcated, generally marked with broad coloured 
