22 On the Melanians of Lamarck. 



rnits Melanopsis and Pirena, placing them after Melania and Ris- 

 soa ; and before Acteon (Tornatella) and Pyramidella. Deshayes 

 (Lam. vol. viii, p. 488,) appears inclined to miite the three genera, 

 for besides placing part of Pirena in Melanopsis, he unites the re- 

 mainder to Melania, into which he beheves Melanopsis can be 

 merged by the gradual disappearance of its conchological charac- 

 ters. Thus there is a great difference of opinion upon these gene- 

 ra, and much of the confusion can be traced 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 pi. xii 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 decoupes." — Desh.) Melania, on 

 the contrary, has the following characters, drawn from M. Vir- 

 ginica. 



Animal with a truncated proboscidiform head, bearing two annulated tentacles, 

 upon an enlargement of the outside basal portion of which 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 footisoval, 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 moUusca 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 preerosa in this genus, and as Ferussac's description of 

 the animal applies pretty well to Anculosa, I will take it for 



* Melania, pi. I, fig. 1 — 2, of my Monograph of the N. American fluviatile uni- 

 valves. 



