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22 On the Melanians of Lamarck. 
mits Melanopsis and Pirena, placing them after Melania and Ris- 
soa; and before Acteon (Tornatella) and Pyramidella. Deshayes 
(Lam. vol. visi, p. 488, ) appears inclined to unite the three genera, 
for besides placing part of Pirena in Melanopsis, he unites the re- 
mainder to Melania, into which he believes Melanopsis can be 
merged by the gradual disappearance of its conchological charac- 
ters. Thus there isa great difference of opinion upon these gene- 
ra, and much of the confusion can be t a ed to the fact that the 
characters of the animal of Melania, instead of being taken from 
an undoubted species, (as M. subulata or Virginica,) have been 
drawn from Pirena aurita, Miil.; which, although it approaches 
Melania in its conchological characters, is generically distinct ; so 
that MM. Deshayes’ and Rang’s generic characters of the former, 
apply to the latter alone. Pirena aurita, (figured as Melania au- 
rita, by Rang, on pl. xm of Guerin’s Mag., 1832,) is represented 
with quite a long foot, which is much extended beyond the 
mouth, and tapering posteriorly ; the tentacles are not annulated, 
the head is scarcely proboscidiform ; and the edge of the mantle 
is fringed—(“ ayant ses bords découpés.”—Desh.) Melania, on 
the contrary, has the following characters, drawn from M. Vir- 
ginica. o , . 
Animal with a truncated proboscidiform head, bearing two annulated tentacles, 
upon an enlargement of the outside basal portion of whic the eyes are situated, 
but never beyond the middle of the tentacle; the mouth is provided with a double 
row of file-like teeth on each side; the footis oval, not extending beyond the muz- 
zle, slightly thickened, and of medium size ; edge of the mantle continuous and 
simple. The exposed parts are colored with blackish lines upon a yellowish 
ground, which run transversely across the rostrum and tentacles.* Oviparous. 
Thus it will be perceived that this genus has scarcely any es- 
sential point in common with those mollusca from the rivers of 
West Africa, of which P. aurita may be considered the representa- 
tive. Melania is more like Paludina, but the distinctions are suffi- 
cient to place them in different, though adjoining families. 
An animal with a fringed mantle can scarcely enter the family 
of Melanians proper, so that P. aurita and its congeners, must be 
placed in another, of which this is, perhaps, the most tangible 
character ; namely, the CeRITHINAE.~ 
I have never seen a living Melanopsis, but as Deshayes places 
Anculosa prerosa in this genus, and as Férussac’s description of 
the animal applies pretty well to Anculosa, I will take it for 
* Mevani, pl. L, fig. het, of my Monograph of the N. American fluviatile uni- 
alves. ™ 
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