MELANOPSIS. 



that are considered by geologists (in this country) to be 

 of marine formation : we know not what degree of credit 

 is to be given to the assertion of a celebrated author, 

 that the greater number of the genera of the Pectini- 

 branchia might formerly have contained species peculiar 

 to rivers and lakes as well as to the sea; but this we do 

 know, that wherever the fossil Melanopsides are found, 

 they are accompanied by many other species of genera 

 that at present only live in fresh water, and therefore we 

 think they ought to be considered as characteristic of the 

 formation in which they occur. 



Shell oblong, fusiform or conico-cylindrical, pointed 

 at the apex when complete, but very frequently decollated 

 and eroded; spire with from 5 to 15 volutions, the last 

 often forming two-thirds of the whole shell; aperture 

 oblong or oval, pointed at its upper parts; columella 

 twisted, solid, callous, separated from the exterior mar- 

 gin at the base by a notch; the callosity spreading over 

 the last volution but one, thicker near its union with the 

 upper extremity of the aperture, where the outer lip is 

 sometimes deeply notched : operculum spiral, horny, not 

 completely closing the aperture. 



The shells which form this distinct Genus have been 

 placed by Linneans in Buccinum, Murex, and Stromhus; 

 Olivier united them to Melania, and Bruguiere placed 

 some of them in Bidimus, and others in Cerithium. We 

 accord with De Ferussac in considering the the two first 

 species of Lamarck's Pirena as true Melanopsides, both 

 on account of the agreement in the characters of the 

 shells as well as the animals. (His P. aurita and granulosa 

 belong to Melania.) 



The Melanopsides, as far as we know at present, are 

 confined to the continents of the old world ; several of 

 them are european, but no one has yet been found recent 

 in Britain : those which Lamarck called Pirencs are pecu- 

 liar to Madagascar. 



Our plate co;itains representations, at 



Fig. 1. Of Melanopsis atruy d'Audebard ; Strombus ater, Linn.; Pirena tere- 

 brans^ Lam. 



2. huccinoidesj d'Aud.; M. Icevigata, Lam.; Melania, 



Olivier. 



3 costata. 



4. acicularis, d'Aud. ; M. Audehartiiy Prevost, from the 



Thernal Springs of Weslau, near Vienna. 



