You could never have anticipated that the Bivalved Mollúsca (Conchífera) would be found among the prey of these carnivorous tribes, than which there are apparently no animals less fitted to gain access to their strong-holds, so that even Blainville has expressed himself incredulous on the point. But the fact is certain, and has been known since the time of Aristotle (Hist. Anim., lib. iv. cap. iv. sect. 148-9.); nor, indeed, is it hastily to be believed that such an improbable statement would have been made by the Stagyrite, had it not rested on personal observation. The Púrpuræ prove extensively destructive to muscles and other littoral bivalves: the Búccina feed upon those which burrow in sand in somewhat deeper water; and it is very probable, considering the similarity of their organisation, that all the whelks and rock shells, and perhaps all the pectinibranchial zoophagous gasteropodes, have the same taste, and an equal capacity of gratifying it. How, you ask, and by what means? Do they glide insidiously, and pop a stone between the valves, to prevent their closure? or do they venture slily to insinuate their foot, and seize upon the unwary inmate? The first they cannot do, and the latter I should deem a hazardous attempt; but nevertheless it is affirmed that the Búccinum undàtum really runs the hazard in its attacks upon the clam (Pécten operculàris), to which it bears a great enmity. This is not, however, their usual method, which is what you might never guess - by boring a hole in one valve through which they reach their miserable victim. On examining a number of valves of dead shells, of Máctræ and Anatinæ especially, you will perceive in many, and generally near the beaks, a small circular hole drilled with a neatness that the gimlet of the artisan could not more than emulate; and these holes are the workmanship of the

"Is commonly taken in dredging by fishermen, who either use the animal for bait, or destroy it, from a supposition that it is very destructive to the large scollop, Pécten máximus, by insinuating its tail (as it is termed) into the shell, and destroying the inhabitant: this, we have been assured, they will do even in a pail of sea water." (Mont. Test. Brit., p. 238.) The mode in which they anciently fished for the Púrpuræ proves the danger. "Now these purples are taken with small nets, and thinne wrought, cast into the deep; within which, for a bait to bite at, there must be certain winckles and cockles, that will shut and open, and be ready to snap, such as we see those limpens be, called mituli. Halfe dead they should be first, that, being new put into the sea again, and desirous to revive and live, they might gape for water: and then the purples make at them with their pointed tongues, which they thrust out to annoy them; but the other, feeling themselves pricked therewith, presently shut their shels together, and bite hard. Thus the purples, for their greedinesse, are caught and taken up, hanging by their tongues." (Holland's Plin., i. 259.)

gasteropodes in question.* Having secured the shell, by applying to it the disk of the foot, they apply, to the point where they mean to penetrate, the apex of their proboscis, and now by a constant rubbing or grating of their filiform rough spinous tongue, assisted, perhaps, by some corrosive quality of the saliva, they succeed ultimately in perforating the shell. Surely the "patientia vincit" [patience overcomes] had never a more remarkable illustration; for the Búccina may work for days, and even weeks, before the life of the animal attacked is fully extinguished.

But the proboscis (fig. 50.), the organ by which this work is effected, demands a more detailed description; for its me

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chanism is scarcely less wonderful than the analogous organ of the elephant. It is cylindrical and of considerable length, and when not in use is kept retracted within the body, where it lies beyond the reach of injury. The better to understand its structure, we may represent it as being formed of two flexible cylinders, one within the other, and which are united at the upper margin, so that, in drawing out the interior cylinder, we can only lengthen it at the expense of the other; and, on pushing it back again, we, in shortening it, give corresponding extension to the exterior, but the latter lengthens only on the upper side, because it is fixed to the parietes of the head by its inferior margin. Let us now add a number of longitudinal muscles, all of them very much divided at both extremities: the stripes of their internal or superior extremity are attached to the parietes of the body, those of the opposite end all along to the internal surface of the inner cylinder of the proboscis; and their action, consequently, is to draw this cylinder and the whole proboscis inwards. When thus retracted, a great part of the internal surface of the interior cylinder makes part of the external surface of the exterior cylinder, and it is just the contrary when the proboscis is elongated and protruded. The protrusion of the inner cylinder by the unrolling of the exterior, or, which is the same thing, the evolution of the proboscis, is effected by its own peculiar annular muscles: these encircle it all its length, and, by con

"The purple hath a tongue of a finger long, pointed in the end so sharpe, and hard withall, that it is able to bore an hole and pierce into other shell-fishes, and thereby shee feeds and gets her living." (Holland's Plin., i. 258.) The ancients were better informed on this subject than some modern writers, who have attributed these operations to the Tròchus. (See Smellie's Phil. of Nat. Hist., i. 396.)

tracting in regular succession, they force it out beyond the lips, in a manner perfectly similar to the evolution of the tentacula of the snail. There is, in particular, one muscle, near the place where the exterior muscle is attached to the head, which is stronger and more effective in this operation than all the others. When extended, the proboscis can be bent to all sides, and at any point, by the action of the retractor muscles, parcels of them acting, while others assume the place and office of antagonists. The figs. 51, 52, and 53. will serve

to illustrate this interesting mechanism. In fig. 51. the proboscis is retracted about a half: the external cylinder (a) is seen enveloping a portion of the inner (6), the end of which (c) is the end of the proboscis: the muscles which draw it within the body (d d) are in a state of contraction, and at e we see the great annular muscle, the use of which is to push forwards the inner cylinder, and consequently lengthen the organ. In fig. 52. this muscle, and all the annular fibres, have by their action greatly protruded the proboscis, and its retractor muscles (d d) are extended and laid bare; the exterior cylinder (a) has become very short, and the interior (b) is proportionably lengthened. Fig. 53. represents the two cylinders cut up in a longitudinal direction to show what they contain, and in what manner the retractor muscles are distributed upon the inner parietes. In the inner cylinder we find the tongue, with all its apparatus (ee), the salivary

canals (ff), and the greater portion of the gullet (gg): the tongue is a very narrow cartilaginous membrane, armed with numerous acute spines or prickles curved backwards; and the principal purpose of the elongation of the proboscis is seemingly to carry its rough point to the body which the snail wishes to perforate and suck. (Cuvier, Mém. sur les Mollusq. M., xvii. 7.)

This anatomy of the proboscis is derived from an examination of the organ in Búccinum undàtum, but it is applicable to all the pectinibranchial or proboscidian Carnívora. The other organs subservient to digestion in this tribe present nothing remarkable in their organisation. The stomach is a membranous bag, irregularly plaited on the inner surface; the intestinal canal, like that of carnivorous animals in general, is short, and the lower portion, or the rectum, the inner coat of which is raised into several strong longitudinal folds, is wide, and opens on the right side of the branchial cavity under the margin of the collar. Cuvier observes that the sides of the rectum are thickened by a whitish substance, fatty, and a little granular, of which the use is unknown.

It appears to be ascertained that the Búllæ are also feeders on the Bivalved Mollúsca. Mr. Humphreys mentions that he had found a species of Mya alive in the gizzard of Búlla lignària. (Lin. Trans., ii. 16.) Cuvier says that the stomach of the Búllæ, in general, is usually filled with the remains of small shells (Mém. sur les Mollus. M., x. 14.) ; and Mr. Sowerby tells us that they are "exceedingly voracious, as is evident from the fact, that the animal of B. apérta is sometimes distorted by having swallowed entire a Córbula nucleus, which is a very thick and strong shell, nearly equal in size to itself." (Gen. Rec. Foss. Shells, No. 39.) Now, as the Búllæ have no perforating instrument in the mouth, nor jaws to crack them, they are under the necessity of swallowing their prey entire, and, as might have been anticipated, there is provided an internal apparatus to supply this deficiency, and break up the shells, so that the inmates may be exposed to the influence of the digestive agents. This singular apparatus is placed within the gizzard, and consists of three strong calcareous pieces, differing in form and size in the different species, thus modified, undoubtedly, to suit them to their peculiar wants, and moved by powerful muscles against each other. In the Aplýsia, a genus of the same natural

* Cuv. Mém., x. 13. These stomachal teeth were described by Gioeni as a new genus of multivalve shells; a genus retained by Retzius, Bruguière, and Lamarck, until the mistake was detected by Draparnaud. (See Bosc, Vers., i. 76.)

order (Tectibránchia) as the Búlla, we find a curious modification of this structure, accompanied, however, with a total discrepancy in the tastes and propensities of the creature; and this is a fact which deserves to be remembered in estimating the value of inferences, in relation to the habits of animals, drawn from their presumed affinities. The oral organs of Búlla and Aplýsia are nearly the same, and there is a resemblance in their complicated digestive apparatus; but, instead of three shells, the muscular gizzard of the latter is studded with numerous sharp pyramidal knobs of a semi-cartilaginous consistence, and of unequal sizes, and which may be rubbed off very easily, for they have no muscles to attach and move them. * When Bohadsch saw this structure for the first time, it seemed to him so anomalous and wonderful, that numerous dissections were required to convince him of its being the natural armature of the organ (De Anim. Mar., p. 19.); and he fell into the erroneous conclusion that it was fitted to triturate the shells on which the animal was presumed to prey. (De Anim. Mar., p. 22.) But the Aplýsia is really herbivorous, as is asserted by Pessonel, Cuvier, and others; and, were it necessary, I could add my testimony to this fact, having at one time kept a large specimen of Aplýsia dépilans for nearly three months in a state of confinement, during which it was fed on Fuci only, and these it ate greedily, showing some partiality to the dulse (Fucus palmatus). The food, previously to its reception in this curious gizzard, has passed through a large membranous crop, in which it probably undergoes little change: in the gizzard it is broken down, and in this state enters a third stomach, armed also on its internal surface with hook-like prickles directed forwards, and intended, doubtless, to tease the fibrous mass, that it may be more thoroughly subjected to the dissolving virtue of the gastric juices, and reduced to a homogeneous pulp, previously to its commixture with the bile, which flows into this viscus from two large orifices close to the pylorus, opening between two small membranous prominent crests. (Cuvier, Mém. sur les Mollusq. M., ix. 18.)

*Pessonel's description of this organ is short, but characteristic:-"The membranes are thick, and are set with twelve stones, or horny pieces, of a bright yellow colour, and as transparent as fine yellow amber, ending in points like a diamond; so that the great side, or basis, is set into the membrane of the gizzard, as a diamond in its socket. Others differ in size, having different figures, that, in acting all together, they may be able to break and grind the herbs the animal feeds upon, as well by the strength of the muscle, or gizzard, which puts them into action, as by the situation of these stones, assisted by grains of sand found in it, turning the whole by this trituration into a liquor." (Phil. Trans., vol. 50., 1758, p. 587.)