Auricula] 



MUSEUM OF ANIMATED NATURE. 



199 



tac-Ies, vvliii-h are contractile, setaceous, very long, 

 and oculaled at their internal base ; mouth tin nished 

 superiorly with a crescent-shaped tooth, and below 

 with a lingual mass armed with small hooks, and 

 surmounted by a sort of veil which is short and 

 notched ; foot oval and rather short ; respiratory 

 orifice on the lelt, upon the collar. 



Shell rather delicate, sinistral, very much rolled 

 or coiled up on the same plane ; concave on each 

 side, the spire re-entrant (renfrant); aperture 

 rounded with a sharp border, and interrupted by 

 the convexity of the whorl which precedes it. 

 (Rang.) 



Mr. Sowerby remarks, that the principal pecu- 

 liarity in this genus appears to him to consist in the 

 fact, that the shells are what are called reversed; a 

 fact doubted by some who have described them as 

 umbilicated above. A careful examination of many 

 of the species, in a living state, satisfied Mr. Sower- 

 by, that these animals carry their shells in a di- 

 rection opposite to that of the turbinated molhisks 

 generally, and that the heart is placed on the right 

 side, and the respiratory orifice on the left, exactly 

 the reverse of their position in most others; but he 

 farther observes, the knowledge of the animal is 

 not necessary to prove this, as the shell itself carries 

 the demonstration, it being only needful to observe 

 on which side of the shell the very apex of the 

 spire is to be seen ; if we take that side for the 

 upper, in conformity with the strict rules of analogy, 

 it will be evident that the aperture is on the left- 

 hand side. We may add that we have now before 

 us a number of shells of Planorbis. in which the 

 mouth turns obliquely to the left, and on that side the 

 apex of the spire is visible ; hence is the shell sinis- 

 tral. This, ho tvever, is denied by some naturalists, 

 and especially M. Deshayes, who contends that 

 the shells are dextral, even those which the most 

 esteemed authors had judged to be sinistral IVora 

 the depth of the umbilicus on the right side. He, in- 

 deed, admits, that with respect to the position of the 

 heart on the right, and the pulmonary orifice, &c. on 

 the left, as L'uvier has remarked, the animal is sinis- 

 trally organized, but he affirms that the other vis- 

 cera are placed as usual, whence he regards the 

 raollusk as really dextral, like Helix, and he adds, 

 "thus the observations of M. Desmoulins explain 

 how in the genus Planorbis appearances place a 

 sinistral animal in a dextral shell, and how in reality 

 the animal is dextral as well as its shell," there 

 being no derangement of organs, excepting with re- 

 gard to the heart and the orifices. 



The Planorbis corneus (Helix corneus, Linn.) is 

 the largest European species, and is found in slug- 

 gish streams, stagnant waters, deep drainage courses, 

 &c. We have lound it common about Reading, and 

 it is, we believe, plentiful about Oxford. We have 

 taken it in the neighbourhood of Hammersmith, 

 in deep clear ditches, where the water-newt was 

 plentilul. 



Montagu, as well as others, have observed that 

 this species yields a very beautiful purple dye, but 

 all attempts to fix it, by means of acids or astringents, 

 have hiiherto proved inefi'ectual. The shell is 

 opaque, of a horny brown colour, with the whorls 

 transversely striated. In fine specimens, the mouth 

 is tinged with pale violet or lilac. 



2627. — The Keeled Pi,anorbis 



{Planorbis carinntus). This species, which is re- 

 markably flat and thin, has the outer edge finely 

 keeled : the colour of the shell is brown. It is 

 very abundant in fresh water, either running or 

 stagnant ; the mollusk is of a slender figure, with 

 long tentacles. Referring to Fig. 2627 : a repre- 

 sents the Shell and Animal of Planorbis carinatus ; 

 6, a mass of the Eggs of Planorbis corneus on a 

 leaf. 



2628.— The Common Physa 



^PhysafontiiicUia:). In the genus Physa the shell 

 is generally sinistral, of an oval or elongated figure, 

 sometimes nearly globular, smooth, delicate, and 

 Tery fragile. The aperture is oval ; the edge of the 

 light lip sharp. The genus is very extensive, species 

 occurring in the fresh waters of the four quarters of 

 the globe. 



The Physa fontinalis is found in the fresh waters 

 of England and the adjacent continent, inhabiting 

 sluggish streams and stagnant waters : we have 

 found it not unfrequently on the under side of the 

 leaves ofthe water-cress and other plants. The shell 

 is smooth, diaphanous, and of a yellowish horn 

 colour ; the spine is short and rather pointed. Col. 

 Montagu, who gives a description of this species, 

 states, that when in motion it covers a great part 

 Ofthe shell with a thin pinnated membrane, thrown 

 out on the right side, extending quite behind and 

 I)artly on the left side, covering the smaller volu- 

 tions: this membrane (mantle) is, he says, very 

 deeply divided, or digitated, the points of which meet 

 and sometimes intersect on the back of the shell, 



and it is so transparent as scarcely to be distin- 

 guished but by the assistance of a glass. The foot 

 he describes as long and narrow, and the foramen 

 on the lett side, " as must be the case with all the 

 animals of this kind inhabiting heterostrophe shells." 

 Col. Montagu concludes his remarks on this species 

 as follows: "It has a very considerable locomotive 

 power, and transports itself by adhering to the sur- 

 face of the water, with the shell downwards : 

 against which it crawls with as much apparent ease 

 as on a solid body ; and will sometimes let itself 

 down gradually by a thread affixed to the surface of 

 the water, in the manner of the Limax filans (' Linn. 

 Tr-ans.' iv., 85, t. 8), from the branch of a tree. The 

 property of crawling underwater, against its surface, 

 is not wholly confined to this species ; but we know 

 of no other testaceous animal capable of suspending 

 itself under water in the same way.* It has the 

 power of throwing its shell about in an extraordinary 

 manner, either in defence or to remove obstructions, 

 continuing at the same time fixed by its foot. Pro- 

 bably this singular motion is sometimes occasioned 

 by a minute species of Hirudo (Gordius inquilinus, 

 Miill., Verm.), which infests this and many other 

 fresh-water testaceous animals ; twenty or more 

 may be seen adhering to its sides like slender white 

 filaments." 



Fig. 2629 exhibits an allied species. Physa 

 Hypnorum : a, the Animal and Shell ; &, the Mass 

 of Eggs, natural size ; c, the same, magnified. 



The eggs of the Physa invested in a gelatinous 

 medium are very common on the leaves or stalks of 

 the water-cress. 



2630. — ^The Common Limn^ea 



{LimntEa stagnalis). In the genus Limnaea the 

 animal is of an oval form, more or less spiral ; head 

 furnished with two flattened triangular tentacles, 

 carrying the eyes at their base, on the internal side ; 

 mouth furnished with an upper piece for mastica- 

 tion, surmounted by a soit of very short veil ; foot 

 oval, bilobated anteriorly, narrowed posteriorly ; 

 orifice of the pulmonary cavity on the right side, 

 on the collar, in form of a furrow, and capable of 

 being covered by a fleshy appendage which borders 

 it below. 



Shell delicate, fragile, of an oval oblong, with a 

 spire more or less sharp and elongated, and an 

 aperture longer than it is wide, oval, sometimes 

 very large, with a sharp edge, not continuous, on 

 account of the convexity of the preceding whorl ; 

 on the columella an oblique plait. 



M. Deshayes observes (last edition of Lamarck) 

 that the animal of Limnaea presents peculiar cha- 

 racters. On the head are two triangular tentacles 

 very much enlarged at the base, and having the 

 eyes rather projecting on the upper and internal 

 part of that base. The head is large and flattened, 

 separated from the foot by a shal low furrow. The 

 foot inclines to oval, terminated in a point poste- 

 riorly, and is delicate and flattened on the sides. The 

 mantle, closed anteriorly and narrow, forms a sort of 

 collar-, as in the Helices. There is a great cavity 

 behind its border. The upper wall of this cavity, 

 delicate and transparent, is covered on its internal 

 srrrface by a very well developed vascular net-work 

 destined for respiration. 



The limnaea is abundant in still or sluggish fresh 

 waters, where it feeds on aquatic plants, up the stems 

 of which it creeps, coming up to the surlace for the 

 purpose of respiration. We have often seen them 

 floating in the reversed position like the Physa; 

 they have, in fact, when so situated the power of 

 locomotion, and may be observed moving their 

 ventral disc, as if crawling along some solid surface, 

 whereas it only acts on the water, of which the sur- 

 face offers sufficient resistance to the vermiform 

 movements of the disc, to enable the mollusk to 

 work its way. The eggs are very numerous and 

 enveloped in a mass of glairy gelatine of an elon- 

 gated ibrm ; they are deposited on stones, or on the 

 leaves or stems of vegetables. The shell is very 

 delicate, and pellucid; the spire is produced and 

 conical. The external colour is brown, but the shell 

 is often covered with a sort of greenish or greyish 

 green calcareous deposit, varying in thickness, as 

 in many specimens now before us ; the cause of this 

 deposit we are unable to explain. The same occurs 

 on Limnsea auricularia. Fig. 26.31 represents the 

 Animal and Eggs of Limnaea stagnatilis : a, the Ani- 

 mal and Shell ; b, the mass of Eggs magnified. 



2632. — The Sprkadiso Limnaea 

 (LimncM auricuhr'ta). This species, distinguished 

 by the shortness of its spine, the capacity of the 

 last whorl, and the extent of the spreading mouth, 

 is common in the same localities as the last species, 

 which it resembles in habits and manners. 



Fossil specimens of Physa, Planorbis, and Limnaea 

 occur in considerable abundance in fresh-water 

 tertiary formations of Europe ; but the number of 



• Tlie Liptopa, a marine shell mollusk, is said to have a similar 

 power. 



distinct species does not appear to be very clearly 

 made out. 



Mr. Lea, in his ' Contributions to Geology' (Svo. 

 Philadelphia, 1833), notices the tufaceous lacustrine 

 formation of Syracuse, Onandaga county. New York. 

 He found the substratum which lined the side ol 

 the canal to consist of a calcareous marl of a whitish 

 colour, bordering on that of ashes, friable, and rather 

 soft to the touch. A subsequent analysis by Pro- 

 fessor Vanuxem proved it to be nearly pure carbo 

 nate of lime. Numerous perfect specimens of the 

 genera Limnaea, Physa, Paludina, and Ancylus were 

 obtained, all being analogous to the species inhabit- 

 ing at that time the fresh waters of that region ; and 

 Mr. Lea states that it was evident that the deposit 

 was caused by the drainage of the lake. The spe- 

 cimens were found to be completely bleached, and 

 were generally in an unbroken state. " A lacus- 

 trine formation of so recent a nature," says Mr-. Lea 

 in continuation, " as this appears fo be, is not, I 

 believe, of frequent occurrence. It is the result, 

 however, of one of those causes which are now in 

 action; and another instance might be mentioned, 

 in which the effect of this cause, though striking, 

 has not advanced to that period when it would make 

 a finished deposit : I mean the small lake, or pond, 

 in Sussex county, New Jersey, well known by the 

 descriptive name of Milk Pond.* Here countless 

 myriads of bleached shells of the families Lymn^ana 

 and Peristomiana, analogous to the species now in- 

 habiting the adjacent waters, line and form the 

 shores of the whole circumference of the lake, to 

 the depth and breadth of many fathoms. Not having 

 visited this interesting lake myself, I repeat what 

 has been communicated to me by intelligent scien- 

 tific friends who have examined it, and on whose 

 report the most implicit reliance may be placed. 

 Such is the quantity of bleached shells now remain- 

 ing there, that thousands of tons of these small 

 species, in a state of perfect whiteness, could be ob- 

 tained if any useful purpose required the removal 

 of them. For agricultural purposes this mass might 

 prove of great utility. One friend, I remember, 

 mentioned to me that he had obtained a sharp 

 pointed pole, which he inserted ten or twelve feet 

 perpendicularly into the mass, on the shore, near to 

 the edge of the water, without its having passed 

 through it. As far as can be ascertained, this mass 

 seems to form the whole basin of the lak£, and it 

 may at some future and perhaps not far distant 

 period form a tufaceous lacustrine deposit similar to 

 that of Syracuse." 



Family AURICULAD/E (AURICULA, 



MELAMPUS, &c.). 



2633.— MiDAs's Ear 



(Auricula Midee). The genus Auricirla differs from 

 those of the preceding aquatic air-breathing mol- 

 lusks in the columella of the shell being marked 

 with decided oblique channels (canelures). The 

 figure of the shell is oval or oblong; the mouth 

 longitudinal, with a reflected lip, or simple. Cuvier 

 says, " we are not certain if these animals live in 

 marshes, as the Limnaea, or only on their borders, as 

 the Succrneae " (Helix pntris, Linn.). One species 

 exists in France along the borders of the Mediterra- 

 nean (A. myosotis). A writer on conchology 

 observes, "The probability is that the auricula 

 lives in the neighbourhood of rivers, lakes, or mo- 

 rasses, and that its respiratory .system, though formed 

 for breathing air, is so framed as to enable it to sus- 

 tain any vicissitudes which such a locality might 

 render likely to occur." 



The Auricula Midae is said to be a native of the 

 East Indies ; Lamarck names the Moluccas as also 

 among its localities. It is a handsome shell, and 

 well known to collectors under the name of Midas's 

 ear. 



2634. — The Cone-shaped Melampus 



(Melampus coniform'is). As in Auricula, the shells 

 of the genus Melampus have salient folds on their 

 columella, but the external lip of the opening has 

 no roll, and is finely striated. The general contour 

 of the shell is that of a cone, of which the spire 

 forms the base. The genus Melampus of De Mont- 

 fort is identical with Conovnlus of Lamarck. 



The Cone-shaped Melampus is found in the 

 rivers of the Antilles Islands. 



ORDER NUDIBRANCHIATA. 



The molhisks of this order are not enclosed in or 

 protected by shells ; they have no pulmonary cham- 

 ber, but the branchise or organs of respiration are 

 seated on some part ofthe upper surface, freely ex- 

 posed to the water. All are bisexual and marine. 

 Many species have the habit of swimming reversed, 

 with the foot, which is concave like a boat, at the 

 surface of the water, and they further assist them- 



* From the milky appearance of ihe waters near the shore, caused 

 by the mass of bleached shells deposited there. In tjordons map ol 

 New Jersey it is named White I'oud. (Lea.) 



