344 CRETACEOUS GASTROPODA 
L. Family —UMUBONTID 41. 
vuponuna&, H. and A. Adams, Gen. I, p. 407; RoreLLap#, Gray, Guide, 1857, p. 139 ; 
ROTELLIN, Chenu, Man. I, p. 353; Globulus, Schum., in Philippi’s Handbuch der Conch., 1855, 
». 208; Umsonips, A. Adams, Ann. mag. nat. hist., 1863, XI, p. 264. 
k 
The animals of the Uszonrip# are as yet very insufficiently known. The 
only reliable description is said to be that of Um. vestiariwm, (var. lineolata) 
Linné, by Gray, in the Ann. mag. nat. hist., IJ. Ser., vol. XII, and Guide, 
1857, p. 140. Taking the organisation of this species as the type, the 
animals of the Umsonmpz#£ are distinguished, from those of all other 
CintpEDATA, by having a very short, retractile proboscis which is surrounded by 
a veil. The radula is linear, long; the teeth in general formed very similarly to 
those of the other CrirpEpaTa, except that the central ones are less denticulated. 
Tentacles are two, linear; right free, simple, with a compressed lobe on its inner 
side; left tentacles with a large membranaceous expansion folded over the mouth, 
and then back to the side of the head, continued by a slight ridge to the lateral 
fringe. Lateral fringe distinct, with three tentacles on each side, produced on 
the front of the right side into a large, oblong, fleshy lobe, which probably covers 
the base of the shell and forms the callosity of the axis (Gray, Guide 1857, p. 189). 
If the basal callosity be formed by the peculiar fleshy expansion of one portion 
of the fringe, the unequal development of the latter may in general be considered 
as a good character, because there is always some sort of a callous ridge to be 
observed even in the sub-umbilicated genera belonging to this family, 
The shells of the Uszonrzp# are mostly orbicular, with a short spire; aperture 
roundish with the outer lip sharp or slightly thickened ; columella thick, generally 
passing into a callous covering at the centre of the base; surface polished, without 
epidermis ; internal layer of the shell pearly. Operculum horny, multispiral.* 
The Umzsonup never seem to have been very numerous. Fossil species occur 
from the paleeozoic deposits upwards, but they are always scarce, though a good 
number of them appears to have been described under the names of Trochus, Turbo, 
Delphinula and others. The jurassic deposits are richer than the cretaceous, in 
specific as well as in generic forms. Up to the date of the last edition of Deshayes’ 
‘ Anim. s. vert., foss. de Paris,’ remarkably few species were known from the tertiary 
strata, and of those which have been reported very few appear to belong to Umboniwm 
(Rotella) proper. The recent species are sparingly distributed in all tropical seas ; 
they burrow in the sand, and their shells are consequently deprived of an epidermis. 
The Umbonium vestiarium is found in the Bay of Bengal on sandy parts of the 
shore, where except the Cytherea casta, Tympanotomus (Cerithium) alatus, 
Philippi, a few species of Purpura and Hemifusus, hardly any other living shells are 
met with, though Foraminifera are very numerous. 
* The operculum of our Bengal variety of Umb. vestiarium is thin, transparent, horny, externally concave, 
internally pyramidally elevated, consisting of very numerous narrow volutions; the margin is very thin, but 
not ciliated ‘i 
