HELMINT 
pofcd of particles of fand, broken pieces of (hell, and 
fea-weed, ^united to a membrane by a-kind of glutinous 
cement; whence.it has very much the refemblance of a 
.coralline. There are tw.emy-five fpecies now afcer- 
-tained, one of which, fabtlla alveolata, is correctly deli¬ 
neated in the Helminthology Plate IV. fig. 20. 
In order to illuftrate more fatisfaftorily. the hifiory 
and economy of the; tvftaceous tribes,'the annexed Hel¬ 
minthology Plate IV. has been conftruftedj from obfer- 
vations made on the living animals in their natural ftate. 
All thofe which inhabit the mufti valve and bivalve 
fliells, are endued with the faculty of opening and fiuit- 
ting them at plea(11 re, for the purpofe of obtaining their 
food and nouridiment; and alfo with a powerful inftinft, 
which, though blind, and imprifoned, yet unerringly • 
direfts them in all their haunts after prey and which, 
on the flighted: touch or difturbance, warns them of 
danger, and excites the inftantaneous doling of their 
valves, and thus foiling an enemy. Their fenfe of 
touch muff be extremely delicate, fince the fined: point 
.communicated ever fo gently to the external part of the 
ihell of a model, cockle, oyfter, &c. direfts them in a 
moment to clofe their valves, and to exert their utmoft' 
•ftrengtlv to keep them Unit. This fenfe appears to be 
communicated by delicate nerves and membranes, and 
.perhaps by the fimbriae which fkirt the fhell; but the 
feat of the fenfes nuift undoubtedly have its place in 
that part of the animal- which refides neared: the hinge, 
as well for its greater fecurity, as for the direction of 
its valves, and the operation of all the included parts ; 
which prefent to the curious pllyfiologift a wonderful 
difplay of the beautiful mechanifm with which the Al¬ 
mighty has formed them. 
Fig. 1, iii the Engraving, prefents a view of the car- 
dium echinatum placed on its bale, with the fiphunculi or 
Typhons.in front, by which it draws in and fquirts out 
the water., the cirrlii or byffus with which, it adheres to 
•extraneous bodies, and the flefliy hook or foot of the 
animal, in the aft of being protruded. 
Fig. 2, reprefents the fame fpecies with the foot or 
hook protruded, in order to take its no.urifliment ; and 
by the help or elaftic force of which it can jerk itfelf 
from .place to place ; and in this manner, when it hap¬ 
pens to be left by the tide, it regains its proper element. 
If touched ever fo gently when lying in this attitude of 
evident enjoyment, it withdraws the hook, and clofes 
in the twinkling of an eye. Lobfters and crabs lie in 
wait.for this opportunity of thru fling in a leg or a claw, 
whereby they kill and fecure the-cockle for-food ; but 
it often happens that the younger ones of thofe crufia- 
ceous .animals; not being fuftieiently hardened or ma¬ 
tured to withstand the violent fnapping of the (hells on 
their clofe, -often lofe the limb ; and herein we fee the 
abundant wifdom and benignity of the Almighty, in 
having bellowed on the cancer tribe the pow er of renew¬ 
ing-their members when cut off; and but for which, the 
whole race would foon become extinft, fince this mode 
of procuringtheirliving fubjects'them to.eterda 1 warfare. 
Fig. 3, is a fine reprefentation of the cardium echinatum , 
as given by Muller, with its top (hell taken oft, dj'fco- 
vering the falciform or I'cythe-fiiape of the animal, when 
its body and foot are expanded in aCtion, and in which 
.pofition it always forms an angle ; the bale of which is 
.the foot, whence fome naturalifts have defcribed the ani¬ 
mal as pediform. The whole is a carneous rounded 
body, ilfuing from among the membranes and lamellae, 
which have their origin near the hinge. This is fe- 
CLired by two ftrong teeth near the beak, and a remote 
lateral one on each fide, locking fecurely into each 
other; thefe eonftitute the Linnaean charafter for afcer- 
taining all (hells belonging to this genus. It has a mod 
beautiful and delicate membrane, which lines the inte¬ 
rior of both the valves, edged with a fine orange-colour 
fimbriae, completely ipclofing the animal when at reft; 
and by the aftion or play of which the valves are un- 
H O L 0 G Y. 355 
queftionably opened and (lint. In this membrane, like- 
wife, the cirrhi or holders'have their origin ; and to its 
bafe the ovarium is fecured. This fpecies is.au inhabi¬ 
tant of mofi of the European Teas. 
Fig. 4, is the lepas fcalpellnm , exhibited in this place 
for the purpofe of (honing the different habitudes of the 
two families comprifed in this genus, viz. balani, dr 
acorn-(hells ; and an at if era, or 'got>fe-(hells. The fpecies 
in the former divifioh are confiantly fixed by their bafe 
to (lone, rock, wood, or other fubftance, where thes' im¬ 
movably grow, as reprefented in Conchology Plate XVI. 
fig. 8. The anatiferse, on the contrary, adhere only by 
a (lender petiole or tendinous tube, which being of a 
foft flexible nature, affords to this divifion the privilege 
of moving or twitting about in a circular direftion in 
fearch of their food. In this figure the fcalpellum is 
fnown in its quiefcent ftate, fixed by its tube, and its 
tentacula or feelers retrafted and at reft. At fig. 5, the 1 
fame animal is reprefented with its tentacula projefted, 
and the valves or (hells fomewhat opened, to receive its 
nouriftiment. It is furnifhed with thirteen valves, fix 
on each fide, and,one at the bacl^, curved, and jndpfihg 
the others. The peduncle is beautifully annulated, 
foft, and fiexible. 
Fig. 6, reprefents the mytilus pholadis, a very curious 
fpecies of muffel, in the aft of opening its valves to take 
its food, and of throwing out its fubulate foot or (pine, 
and the byffus or threads with which it adheres to ex¬ 
traneous bodies. Fig. 7, difplays the fame animal fully 
expanded ; its foot or hook projefted, and its byffus or 
beard of filky filaments crifped up, as it always appears 
when not attached or (licking to any foreign body. The 
trunk or fyphon of this animal is divided into two tubes 
or orifices at its extremity, which are its mouths, oft-a 
bright red colour, and finely ciliated; the body is car- 
neous, of a whiti(h yellow colour, and when fwollen 
out appears to be too large for its (hell. It inhabits the 
North Seas. 
Fig; 8,'is the ojlrea fuci, or pc Elen Jlriatus of Muller, a 
fmall fpecies o( (callop, generally found among fuci or 
fea-weeds. It is here delineated in the aft of affixing 
itlelf by its filaments or byffus to fome extraneous body, 
its (iphunculus exferted, and its fimbriae expanding 
for the purpofes of nutrition. Fig. 9, dhows the valves 
laid open, to demonftrate the internal (trufture of-the ani¬ 
mal, which is reprefented in a retraftile quiefcent (late, 
the byflus crifped up, the carneous body, ligu-la, and fim¬ 
briae, contracted and at reft ; and the ovarium of a fplen- 
djd red, partly covered with a delicate membrane. 
From the ovarium the young are excluded completely 
formed; and by the help of a magnifier, the joinings of 
the little infant fliells can be diftinftly feen, with all 
their parts as perfeft as the parent animal, though ap¬ 
pearing to the naked eye only as a minute point.—Such 
are the inftinfts and habitudes of the two rirft orders of 
the teftaceous animals. 
The inhabitants of the univalve (hells, pofl'etting a 
lefs complex arrangement of parts, are. more fimple in 
their nature, as well as in the (trufture of their dwell¬ 
ings. The helix, or domeftic fnail, in its habits and 
economy, at once difplays the manners and inftinfts of 
the whole univalve tribe. See the article Helix, p. 
327. This clal's is certainly more expofed to a devour¬ 
ing enemy than the bivalves; becaufe they can never 
perfeftly clofe their (hell, but only by a (light opercu¬ 
lum or lid at its mouth ; and even this is not conftant in 
all the genera. Befides, the univalve animals are for the 
mod part extremely flow in advancing from, and retiring 
into, their (hells; whereas thofe of the bivalves are al° 
together as,nimble and expert. In their mode of pro¬ 
pagation, however, a v (lrift (hnilarity prevails, fince they 
are in general oviparous, with very few instances of the 
viviparous kind. One of thefe, however, we (hall il¬ 
luftrate, as being-highly curious. 
Fig. 10., is a correft reprefentation of the viviparous 
J fnail j 
