38 MOLLUSCA. 



increase of the whorls of their shell, the convolutions of which arc 

 nearly in one plane, and because the aperture is wider than it is high. 

 It contains an animal with long, thin, filiform tentacula, at the inner 

 base of which are the eyes, and from the margin of whose mantle 

 exudes a quantity of a red fluid, which is not, however, its blood. Its 

 stomach is muscular and its food vegetable, like that of the Limnsei, 

 of which, in all our stagnant waters, it it the faithful companion. The 



LIMN^EUS, Lam* 



Separated from the Bulimi of Brugiere by M. t>elamark, have, like a 

 Bulimi, an oblong spire and the aperture higher than it is wide ; but 

 the margin, like that of a Succinea, is not reflected, and there is a 

 longitudinal fold in the columella, which runs obliquely into the 

 cavity. The shell is thick ; the animal has two compressed, broad, 

 triangular tentacula, near the base of whose inner edge are the eyes. 

 They feed on plants and seeds, and their stomach is- a very muscular 

 gizzard, preceded by a crop. Like all the Pulmonea, they are her- 

 maphrodites, and the female organ of generation being far from the 

 other, they are compelled so to copulate, that the individual which acts 

 as a male for one, serves as a female for a third ; long strings of them 

 may be observed in this position. 



They inhabit stagnant waters in great numbers ; they also abound 

 with the Planorbes in certain layers of marl or calcareous strata, 

 which they evidently prove were deposited in fresh waterf. 



PHYSA, Drap. 



The Physae, which were placed without any just motive among the 

 Bullae, have a shell very similar to that of a Lymnaea, but without the 

 fold in the columella and reflected edge, and very thin. When the 

 animal swims or crawls, it covers its shell with the two notched lobes 

 of its mantle, and has two long, slender and pointed tentacula, on the 

 greatly enlarged internal base of which are the eyes. These are the 

 small mollusca of our fountains. 



One of them, Bulla fontincdis, L., which is sinistral, is found 

 in France*. 



According to the observations of Van Hasselt, we should place 

 here the 



SCARABJEUS, Montf. 



Which has an oval shell, the aperture narrowed by projecting and 

 stout dentations on the side next to the columella, as well as towards 



* Hel. slagnalis, L. of which H.fragilis is a variety ; H.palustris ; Htperegra ; 

 H. limosa ; //. nuncularin. See Drap., pi. ii, f. 28, 42, and pi. iii. f. 1,7. 



f The mantle of the Limn, glntinosiis, like that of the Physae, is sufficiently ninple 

 to envelope its shell. It is the genus AMPHIPEPLEA. Nilson, Moll, sure. 



J The neighbouring specie*, KvU. hypnnrum, L., and Physa acu/a, and Scafurit/inum, 

 Drap., require an examination of their animals. Vide, Drap., p. 54, et scq. 



