84 ZOOLOGY. 



genus seems to be confined to the rivers of I^orth America. Eafinesqiie's 

 generic name Leptoxis was published two years before Say's Anculom. 

 Some authors suppose the former to be* a genus of Physida?, but the 

 question is settled by some manuscript drawings of the former author, which 

 represent the shell, tentacles, and operculum of Anculosa. 



Ifelanojms is allied to Anculosa, and the species seem to be confined to 

 Europe. It is probable that the few described species of European Melania 

 belong in reality to Melanopsis. 



Say's Melania arinigera (and also Lea's M. dxdtonana and M. Catenoides)^ 

 belongs to Eafinesque's genus Pleurocera^ in which there is a short straight 

 canal anteriorly, and when this canal is lengthened as in Fusus, the genus 

 lo of Lea is the result. Strejxrma of Eafinesque (or Ceripliasia of Swainson) 

 are slightly different forms, in which the aperture and the vertical plane 

 formed by the anterior portion of the whirls, bear some resemblance to the 

 same parts in Cerithium telescopium. 



Fusus fluvialis of Say is the type of /o, and as it would be an anomaly 

 to find a genus so decidedly marine as Fusus inhabiting fresh waters, it 

 becomes a matter of interest to know the animal of the American shell. This 

 was observed in 1841, in its native waters in Holston, Powel's, and Clinch 

 rivers, in eastern Tennessee, by Ilalderman, who made a drawing of the living 

 animal. Its characters and habits are not those of Fesus, but of Melania 

 proper, as distinguished from Leptoxis ; for although it inhabits the rapids 

 as well as quiet M'ater, in both cases it avoids the current by seeking shelter 

 beneath shelving rocks, or in hollows or crevices in them. The head is 

 large, and w^itli the tentacles much exposed ; the foot is as large as in 

 Melania ; the coloration is the same (black lines upon an orange ground) ; 

 the operculum is subspiral as in Melania, the mantle extends into the canal of 

 the shell, but does not form a closed siphon ; the vent is upon the right side ; 

 the mouth is a longitudinal slit ; the eyes (which are sensitive to the light) 

 are upon a short enlargement of the outer base of the tentacles, which may 

 be a little longer than in Melania, and they are not visibly annulated. 

 It differs from Fusus, and resembles Melania in living upon vegetable food ; 

 and it moves along in a sluggish manner, moving the head from side to side 

 upon the bottom. To spinosa and I. tenebrosa, are merely varieties of I. 

 flumalis. The spinose individuals are much the most abundant, although 

 the species is rare when compared with various species of Melania. 



Quoy and Gaimard, to whom the science of Malacology is indebted for a 

 knowledge of the animals of many shells, have figured a number of species 

 as belonging to Melania, the shells of which cannot be distinguished from 

 those of that genus, whilst in the figures the mantle is represented as 

 scolloped. Similar species were drawn in the course of the United States 

 Exploring Expedition. These sj^ecies must be j)laced in the family 

 Cerithiidse. 



Farn. 2. Cerithiidce. The genus Cerithium {jpl. 75, figs. 105-109) are 

 remarkable for the great number of species both recent and fossil (tertiary) 

 which it contains. The animal has the general character of Melania, except 

 that the mantle is scolloped. 

 288 



