346 - CRETACEOUS GASTROPODA 
anterior termination. The aperture also is not sub-quadrangular, as shown in 
d’Orbigny’s figure, but round. The total separation of the aperture from the cavity, 
which is formed by the raised edge of the callosity on one, and by the inner lip on 
the other side, distinguishes this genus readily from Camitia of Gray. I do not 
know any other genus which, as regards this peculiar form of the umbilical callus, 
could be better compared with Lewisiella, than Lewisia which has been proposed by 
Mr. Chitty for a number of species of Stoatostoma, like St. Philippianum. The 
edge of the callus is only so far different, as it is not thickened on the anterior end of 
the inner lip, though on the whole more prominent in front. The genus Cynisca, 
H. and A. Adams, (Ann. mag. nat. hist., 1864, VIII, p. 248) has a similar, 
spirally twisted callous edge, but these shells are spirally ribbed and the outer lip 
externally thickened (vide fam., Zzormpx). Teinostoma wmbilicare, Desh. (Anim. 
s. vert., foss. de Paris, 2me. ed. Vol. II, pl. 63, figs. 27-29) may possibly be 
a Lewisiella. 
4. Oamitia, Gray, 1840 (H. and A. Adams’ Gen. I, p. 409). Shell depressed 
like Umbonium, but the columellar callosity has a twisted edge in front, which ter- 
minates with a tooth in the aperture, with which the cavity of the callus communicates. 
We do not know any fossil species belonging to this genus. 
5. Chrysostoma, Swainson, 1840 (H. and A. Adams’ Gen. I, p. 410). Shell 
sub-turbinate, solid, smooth, inner lip thickened, the end of the columella covering 
wholly or partially the umbilical region, but not expanding over the same, outer 
lip obtuse, not enlarged. There is only one recent species, Ch. paradoxum, known 
from the eastern seas, but in a fossil state the genus has a large number of repre- 
sentatives, especially in the triassic and jurassic deposits. 
The Zeimostoma Wateleti, Desh. (Paris foss. 2me ed., Vol. II, pl. 63, figs. 37-39) 
from the Paris basin is more probably a Chrysostoma than a Teinostoma. 
6. Teimostoma, H. and A. Adams (Gen., I, p. 122, and II, p. 615). Shell 
orbicular, polished; columella terminating with a more or less expanded callus ; 
aperture with the margins obtuse and usually somewhat enlarged or produced at 
the periphery. The Teinostomata are generally shells of small size, white, polished 
and subvitreous. They appear to be very numerous on sandy coasts of tropical 
seas, and are distinguished from the true Umbonia by their usually enlarged aper- 
ture, with its obtuse or somewhat thickened margins. A. Adams has described, 
since the publication of the “Genera,” many new species from the eastern seas 
(vide Ann. mag. nat. hist., 1863, XI, p. 267, etc.). I have already mentioned, 
that some of the species, described by the same author under the name Hthalia, 
very probably belong to Teinostoma. 
Tn a fossil state these little shells have been as yet only insufficiently 
observed, though there can be little doubt, that farther researches will increase 
their number very considerably.* A few species are described by different authors 
* Hornes does not describe a single species from the Vienna basin, but since the publication of his 
valuable work, in more extended washings of sand and clay, searching for Foraminifera, Bryozoa, &c., 
several of these little shells have been found, 
