1830 .] 
Description of the Animal of Melania. 
21 
satisfactory results than a globular one, in as much as the globe has, of all solids, the 
least surface in proportion to its quantity of matter. Now it is through the surface 
that the cooling process is to take place. Fourthly , I should have preferred a me- 
tallic to a glass surface. It appears by the experiments of Gay Lussac and of pro- 
fessor Leslie that metallic surfaces have a greater attraction for water, in the liquid 
state, than glass; and I have verified the fact myself, having repeatedly obtained de- 
position on a metallic surface that had its temperature 1 0 higher than a glass one 
undewed. The non-conducting nature of the glass is an objection, although, perhaps, 
not so great as might be at first thought, as the heat of the thermometer is also to 
be abstracted through glass. 
In conclusion, I may say, that, perhaps, the arrangement I have suggested in the bo- 
dy of this letter, may be as convenient as Mr. Adie’a : it will certainly be as accurate. 
If made of metal it might be preferable. This point, however, requires some further 
elucidation. 
V . — Description of the Animal of Melania, 
*4. genus of fiuvicttile Testacea ; with remarks on its habits, and the characters office 
species inhabiting the fresh waters of the Gangetic Provinces. 
The following description of the animal inhabiting a shell, regarding which Cu- 
vier remarks “ on commit pas bien 1’animal,” will hardly require further, apo- 
logy for its introduction. The only notice of the animal, given by Lamarck, in his 
description of the family to which it belongs, is contained in the statement that the 
shells of which it consists have two tentaculse and a horny operculum, a descrip- 
tion which is rather vague, and calculated to lead to its classification with many 
testacea very differently constructed. 
Melania. Animal with two setaceous tentaculae proceeding from the broadest 
part of the head, tentaculas bearing the percipient points' on their upper sides, at 
a short distance from the base. 
Head pandnriform ; snout elongated, hilohed anteriorly ; the mouth occupying 
the sinus between the lobes, and extending longitudinally underneath; lobes short, 
rounded. 
Foot or disk subquadrate, rounded posteriorly, anteriorly clypeate, punctate un- 
derneath. 
Mantle furnished with short filiform processes 2 , which clasp the right lip while 
the animal is crawling, perhaps occasioning the transverse furrows observable on 
the exterior of the shell. 
Operculum horny, thin, concentric lamellar. 
In the position of the percipient points, Melania differs considerably from Palu- 
dina, which also has two tantaculae furnished with percipient points. In Melania 
they are situated on the posterior or upper side of the tentaculse, which are not dis- 
proportionately swelled below the points ; while in Paludina they are salient from 
the exterior side of the tentacuke, which appear as if double below them. 
The Melanise are found in sandy and gravelly parts of rivers, seldom m clay or 
mud. They appear to delight in clear streams, and are partial to a shelving shore 
shaded by a high bank. I have never met them in jheels or standing waters, so 
that thev may be strictly called fluviatile. Their occurrence in the great lakes of 
North America does not militate against this fact, as those waters are connects y 
,S “?£ was taken front the small species of the Betwa and 
Cea, as I did not examine minutely the atumal oft ?* ‘^Vriated 
IIIuL III I M II.V1 i V# WpUVIVfUV - 
lu^'an^pMrhinity^f'toking'them'alhre- I cannot °bservi^ thejfin^ri^ted 
mantle, which the smaller species exhibit ; but, trom the dark coleu species of 
the exterior of the shell, it may easily have escaped observation. The large species ot 
Paludina exhibit, at times, the same appearance on the mantle. I have t b 
to discover in Melania the breathing tube whtch, in Ampulla™, is formed by the man 
tie. 
