22 



MOLL USC A. 



tor, coluraella straight ; surpassing the base of the right mar- 

 gin : destitute of an operculum. 



Itinthena erigua. PI. 17. f. 59. The animal is destitute of 

 au operculum, but the under surface of its foot is provided with 

 a vesicular organ resembling a foamy bubble, but which is, in 

 tart, composed of a solid substance, which prevents it from 

 crawling, but enables it to float on the surface of the water ; 

 the lieitd is provided with a cylindrical proboscis, terminated 

 by a vertically cleft mouth, and armed with little hooks, and is 

 furnished with a bifurcated tentaculum on each side. 



FAMILY VI. NERITACBA. 



Shells semiglobular or oval, destitute of a columella ; and the 

 left margin edged and transverse ; provided with an opercu- 

 kim i inhabit fresh waters and the sea 



Natica monilifera. PI. 60. f. 35. A front view, with tentacu- 

 lar head and mantle reflected ; c, the head ; f. 37, a view of the 

 head from beneath ; f. 38, one of the cartilaginous jaws. 



.\iritiiui rhiriutilii. PI. 60. f. 18. The foot in the animal is 

 shorter than the shell ; the head cylindrical and notched by a 

 furrow, and provided with two long pointed tentacula, with 

 the eyes sessile at their base. 



FAMILY VII. PERISTOMIDA. 



Shell conoid or sub-conoid with an operculum, and the mar- 

 gins of the aperture united. All the species are tiuviatile, the 

 animals respiring in water. 



Pahidina impura. PI. 60. f. 11. The animal has two linear 

 subulate tentacula, with eyes at their base ; the mouth trian- 

 gular ; the foot sub-triangular ; and the branchiae composed of 

 tufted filaments. 



Paloata pitcinalit. PI. 60. f. 61. 



FAMILY VIII. MBLANIDBS. 



The margins of the aperture disunited ; and the right one 

 edged ; animal provided with two tentacula. 



Pirena Madagascarensis. P). 17. f. 67. 



FAMILY IX. LYMN.ECEA. 



With an oblong acutely tapering spire, generally smooth on 

 the external surface, and having the outer margin of the aper- 

 ture always acutely edged, and not reflected. Animal amphi- 

 bious, generally destitu:e of an operculum ; and the teiitacula 

 flattened. 



Lynrntfa stagnalis. PI: 60. f. 4. The animal provided with 

 two compressed, broad triangular tf ntacula, near the base of 

 whose inner edge the eyes are situated. They feed on plants 

 and seeds, and their stomach is a very muscular gizzard, pre- 

 ceded by a crop. 



FAMILY X. COLIMACEA. 



Shells acutely spiral, with no projecting parts on their exte- 

 rior, except the markings of their periodical additions ; the 

 right margin of the aperture frequently reflected outwards ; 

 the tentacula are cylindrical, and usually four in number, but 

 two in others : and destitute of operculum. They are terres- 

 trial animals. 



Cvclostoma elegant. PI. 60. f. 10. The animal is provided 

 with two cylindrical tentacula terminated by blunt tubercles, 

 with eyes situated at their external base, placed on two ob- 

 tuse tubercles ; and provided with a horny operculum instead 

 of branchiae. The animal has merely a vascular network 

 spread over the parietes of its pectoral cavity. See article 

 Conchology, Vol. II. p. 376. 



Succinea amphibia. PI. 60. f. 58. With four tentacula, two 

 short and two longer, at the tips'of which are placed the eyes ; 

 each of the tentacula are furnished with a ring near the mid- 

 dle, below which they are thicker to the base. 



Puna texdentatta. PI. 60. f. 67 



Helix tupena. PI. 60, f. 15 ; f . 92 shows the apparatus con- 

 nected with Helix Pomatia; f. 65, toothed cartilage of do. 



ORDER IV. GASTEROPODA. 



Body never spiral, destitute of any shell, provided with 

 a muscular foot attached its whole length under the belly, for 

 the purpose of locomotion. 



Some of the animals of this division are naked, and destitute 

 of any calcarious covering ; others are provided with a dorsal 

 plate; and a third series have a shell which is more or less 

 concealed in their mantle. The animals of this order are 

 limited by Lamarck to those whose bodies are straight, and 

 never spirally convoluted, and which are provided with a mus- 

 cular disk or foot, united to the body nearly its whole length. 

 F. 66, pi. 60, exhibits the nervous system of the Aplysia; f. 67 

 Clio Borealii; f. 67, do^ii the act of swimming. 



SECTION I. PNEUMOBRANCHIJE. 

 Branchiae in the form of a vascular net on the wall of a par- 

 ticular cavity, opeping by a hole, which the animal contracts 

 and dilates at pleasure. 



FAMILY I. I, IMAGINE. 



Branchiae in the form of a vascular net on the partition of a 

 particular ravity, the aperture of which the animal can con- 

 tract or dilate at pleasure. The body of the animals is elon- 



gated, and thry crawl by mean!) of a ventral disk bordered oil 

 the sides by a very narrow mantle. 



f'ltrina beryllina. PI. CO. f. 7. The body of the animal is 

 too large to be completely drawn within the shell ; the mantle 

 is provided with a double border, the upper one, which is di- 

 vided into several lobes, extends considerably beyond the shell, 

 and being reflected over it polishes it by friction. 



Tettacella Scutulum. Pi. 60. f. 6. Body oblong, with a 

 shell at the posterior extremity; four tentacula; the eyes 

 placed in the longest pair ; anal opening at tne posterior ex- 

 tremity. 



Limax ater. PI. 32, f. 25. Body black, rounded above and 

 rugous towards the tail. Limax agrestis. PI. 60, f. 5. 



Onhidium Typha. PI. 32, f. 7. Body oblong, and margined 

 on both sides by the mantle; tentacula two, cylindrical and re- 

 tractile : mouth without jaws, and with two annular appen- 

 dages. 



SECTION II. HYDROBRANCHLE. 

 FAMILY II. LAPHYSIACEA. 



The branchiae are situated in a particular cavity towards the 

 posterior part of the back, and covered by an opercular scutel- 

 lum ; they are provided with tentacula. The animals of this 

 family resemble large snails, but have a thicker body, and are 



broader towards the posterior part, and have a larger margin 

 to their mantle ; the head projects, and is provided with four 

 teiitacula, two of which are placed near the mouth, and the 



other two more behind. The branchial scutellum is corneous 

 or cretaceous.^ 



Dolabella cattota. PL 17. f. 88. Body oblong, narrowed be- 

 fore, widened posteriorly with the borders of the mantle folded 

 over the back ; provided with four semituhular teutacula set 

 in pairs ; branchial operculum inclosing a shell ; anal opening 

 situated near the branchiae. 



Lapliysiadepliam. PI. 32. f. 8. pi. 60. f. 17. Body oblong con- 

 vex, with a large mantle bordering it on each side, which covers 

 the back while in a state of repose ; head with a neck at- 

 tached ; and with four tentacula disposed in pairs ; branchial 

 operculum inclosing a shell; anal opening placed on the 

 back, near the branchiae. 



FAMILY III. BULL ACE A. 



Head very indistinct : the branchiae are situate in a particular 

 cavity, towards the posterior region of the back, and covered 

 by a mantle ; they are destitute of tentacula, and branchial 

 operculum. Some species are unprovided with either exterior 

 or interior shell ; and in others the shell is completely concealed 

 in the mantle ; and there are several which have an external 

 shell attached by a muscle. 



Bulla hydatis. PI. 60. f. 86. Body oblong ovate, slightly 

 convex, divided into two transverse portions, with the mantle 

 folded posteriorly ; branchiae covered ; anal opening on the 

 right side ; body behind covered with a shell. This figure ex- 

 hibits the back of the shell, with the lateral fin-like membranes 

 protruded a. F. 87. The gizzard magnified, a, a, a, the tips 

 of the plates covered by a thin membrane, and surrounding a 

 muscular integument, thickened at the upper part b ; the part 

 attached to the mouth c, with the oesophagus communicating 

 with the gizzard ; d, the intestinal canal. F. 88. The gizzard 

 laidopen at its anterior end, showing the three corrugated cor- 

 neous plates e e e, with their connecting ligaments/, magnified. 



Bulla aperta. PI. 60. f. 83. Lateral lobes of the foot 

 tliickened and reflected upwards ; head indistinct ; destitute of 

 tentacula ; branchiae dorsal ; shell concealed in the mantle, a. 

 (. 84, the gizzard composed of three testaceous plates, showing 

 the smaller plate b, with the connecting ligament c. f. 85, 

 another view of the gizzard, showing the two larger plates d d, 

 with their connecting ligaments; e,th'e gullet ;f, the alimentary 

 canal. F. 68, cutting teeth. 



FAMILY IV. CALYPTRACEA. 



The branchiae are situate in a cavity on the back near the 

 neck, and projecting beyond or included in the cavity ; shell al- 

 ways placed exteriorly. 



Ancylus fuviatilit. PI. CO. f. 9. Body covered by a shell ; 

 two compressed slightly truncated tentacula, with the eyes sit- 

 uated at their internal base; the foot short and elliptical, a 

 little narrower than the body. They are small animals, and 

 found on aquatic plants in slow running streams or lakes. 



FAMILY V. SEMIPHYLLIDIACEA. 



The branchiae are situated under the margin of the mantle, 

 and disposed in a longitudinal series on the right side of the 

 body ; respiring in water. 



Pleurobranchut plumula. PI. GO. f. 14. Animal with an oval 

 fleshy body, covered by a mantle; the foot is broad, and 

 equally margined ; the branchiae are placed on the right side 

 situate in a canal; mouth anterior and placed below in the 

 form of a proboscis ; two cylindrical tentacula, which are longi- 

 tudinally cleft on the external side. Shell internal, thin and 

 obliquely flattened, and lodged in the back. 



PI. 60.' f. 22. Alimentary canal; a the first stomach; c the 

 second stomach ; d the third stomach ; 6 the fourth stomach. 

 The oesophagus dilates into a membranous crop a; at the lower 

 part of which, b, the bile is poured in. It communicates by ;i 

 narrow cardiu with the second stomach c, which is a gizzard 



