Descriptions of New Fluviatile Shells. 83 



and the Sequatchee, two rapid, noisy, rocky streams, favorable 

 to that genus, which cannot bear a sluggish, muddy river at all. 

 I never found Anculosce, even when abundant, save in the 

 most rapid current of a stream, where they cling to the stones 

 or rocks, generally in quite deep water. They cling to 

 these stones with no ordinary tenacity, and it requires some 

 exertion often to dislodge them. As one might suppose, their 

 peculiar fondness for the most rapid parts of the most rapid 

 rivers is not favorable to perfection of specimens; and hence, 

 in this genus, the erosion of the apex forms, in most cases, a 

 conspicuous character. The Io seems to be closely allied to 

 the Anculosa in this respect, and inhabits deeper water. Geese 

 are said to devour the Melanice. in great quantities, and often 

 to suffer from the abundance of such a diet. 



Should his life and strength be continued, the author hopes, 

 in due season, to furnish a complete monograph of the Me- 

 lanidas of the United States, in which an attempt will be 

 made to establish the true species, to rectify the nomenclature 

 of those regarded as erroneous, and to perfect such previous 

 descriptions as were founded on insufficient material. 



l. Melania athleta. 



Plate II. Fig. 1. 



T. conica, subglabra, fusco-cornea, juxta suturas pallidiore; spira 

 elevata; anfractibus 10, sabplanis, obscure plicatis, plicis deorsum obso- 

 lescentibus ; suturis impressis ; apertura ovata, intus albido-rubescente ; 

 columella incurva, in sinuin tenuem producta. 



Shell conical, nearly smooth, dark horn color; spire much 

 elevated; whorls 10, nearly flat, with faint longitudinal ribs, 

 most distinct on the upper part of the whorls ; sutures well 

 marked ; aperture small, ovate, within whitish, tinged near the 

 base with rose; columella rounded, and forming a slight sinus 

 at base. 



