\ 
MONTAGUE’S BRITISH SHELLS. 
ter could not overlook; both these authors 
have described and f gared it. 
¢* That these animals therefore belong as 
much tc the vermes testacea as many of the bul- 
la, there is no doubt; but it was not thought 
necessary at present to forma new genus on 
purpose, for a shapeless shell of irregular 
growth. 
-#¢ Tt is usually somewhat oval, sometimes 
flat and thin, with amembranaceous margin ; 
others are half as thick as they are broad, 
and rarely possessed of any concavity: colour 
silvery-white, or of a micaceous appearance ; 
the upper side is a little convex, andslightly 
wrinkled concentrically to the smaller, or pos- 
térior, end: the cer part is sometimes 
rough, and granulated with crystal-like shin- 
ing angles. 
«© This shell is the lapis limacis or snail- 
stone of authors, and is said to have been 
used for medical purposes: according to po- 
pular opinion, it cures the tertian ague, if fas- 
tened to the patient’s arm.* 
«* Favanne has figured several species of li- 
max in his Zoomorphose, tab. 76, that 
appear to be the intermediate link between 
such as ‘possess an internal shell, and those 
with testaceous covering; these have only 
a small shell attached to the posterior end. 
But as no such have been discovered in Eng- 
land, we only mention it to shew the nice 
gradations in nature’s work ; and how utterl 
unpossible it is to divide that chain, pita f 
she has so admirably linked together.’ 
The cyprea pediculus of Pennant is 
separated from the pediculus of Lin- 
nzus on the authority of Dr. Solander, 
whose trivial name, arcticus, is adopted : 
and it is doubted whether the pediculus 
of Borlase and Donovan, not uncommon 
on our shores, be not also a different 
species, on account of its wanting the 
sulcus on the back, so invariable in the 
foreign ones. ‘To this genus are added, 
the bullata and the voluta; the former 
doubtful whether only a variety of the 
pediculus; the latter found in the West 
Indies, but never before given asa Bri- 
tish shell, though it is sometimes taken 
alive by the oyster dredgers in Saleomb 
Bay. Its animal when alive extends a 
thin membrane from each side the aper- 
ture, and almost covers the shell. The 
pediculus has the same property to a 
great degree, and when in motion under 
water has a very elegant appearance, 
from its diversity of colours. 
_ Under the genus bulla, Mr. Monta- 
gue is rich in information concerning 
the animal inhabitants. ‘The curious 
gizzard-like substance found in the lig- 
garia has been described by Mr. Hum- 
$59 
phreys inthe 2nd vol. of the Linnzan 
Transactions. The extraordinary struc- 
ture of three other species is so well de- 
scribed in the present work,that we can= 
not resist the temptation of iaying before 
our readers the account ef the halio= 
toidea. 
«© The animal, like that of the preceding 
species, so completely envelopes the shell, that 
not the least appearance of it is to be disco-= 
vered, either in a dead or living state. Itis 
of an oval shape, and of a reddish, or brown 
colour; sometimes nearly white: has much 
the appearance of a contracted, naked limax, 
and indeed seems to be nearly allied to that 
class of animals, 
«© The upper part of the body is very con-= 
vex, covered with a thick, tough, ligamen- 
tous skin, that conceals the shell, and extends 
downwards on each side, where the edges are 
thin, and detached from the body: in the 
fore part of this margin is a sinus, through 
aie the animal protrudes an appendage, or 
arm, somewhat flat, a quarter of an inch in 
length, the extremity of which is bifid; the 
lower division terminating in a thread-like 
process. The body of the animal beneath, or 
rather the sustentaculum, is oblong and flat, 
with a deep depression between it and the 
marginal skin: the head is furnished with 
two small) white tentacula, at the base of 
which, are two small black eyes. 
<< The shell may be felt under the skin on 
the back, but is dillicult to be extracted with- 
out breaking, from the extreme toughness of 
the part that covers it ; the best method of ef- 
fecting it, is to make a longitudinal incision 
on the back, with a. pair of sharp pointed 
scissars. 
«« The animal is possessed of considerable 
locomotive power ; and when in motion, 
frequently contracts the margin or loose skin 
into wrinkles, or folds, exposing the sides of 
the body. 
“‘Jt isin size three times as large as its 
shell, and is incapable of much contraction, 
orexpansion : at first sight might be mis- 
taken for the animal of B. aperta, but on com~ 
parison, will be found essentially different ex- 
ternally, and more particularly in being desti- 
tute af the testaceous HE so remarkable 
in that animal. 
«In the singular circumstance of the shell 
being enclosed within the animal of some of 
this class, there is a considerable analogy be- 
tween them and the laplysia. The L. de- 
pilans, possesses a flexible, corneous sub- 
stance under the skin on the back, termed a 
shield ; which differs only from these species 
of open bulla in not being of a testaceous sub- 
stance: this is of an oval shape, pointed at 
one end, which turns inward, anda little to 
one side, in a sub-convulated manner: it is 
* Encyclopzdia Britannica. 
