114 AMERICAN JOURNAL 



fusvs, with a, well-defined sinus or cleft near the top of the 

 outer lip, while the inner, though thin, is somewhat thickened 

 above.' The other characters named by him are such as are 

 generally considered rather specific than generic, and the 

 pleurotomose cut in the outer lip. as applied, to a fluviatile 

 univalve, is altogether sufficient to indicate a new genus. 

 The specimen alluded to by Swainson, and from which his 

 generic description was drawn, was an imperfect one ; and the 

 species has not since been identified by American naturalists. 

 This is less to be wondered at when we consider how very 

 local the genus has always been, and how few specimens have 

 found their way into our collections. The waters of Alabama 

 have as yet monopolized this interesting genus, ; and it is 

 probable that even there it is confined almost, if not quite, 

 exclusivel}' to the Coosa and its tributaries. 



" On p. 342 Swainson gives the following generic description, 

 adding a figure: — 



" ' Fusiform, longitudinally ribbed; a deep sinus at the top 

 of the outer lip ; base contracted ; channel wide.' 



" Mr. Swainson's figure is quite unsatisfactory. His genus 

 Melatoma is referred doubtfully to Clionella by H. & A. Adams, 

 and has not prevailed for this genus in America or Europe. 

 I have, therefore, decided not to make use of it in this case. 



"Subsequently this genus has been noticed by various au- 

 thors, and other names have been applied to it. In 1841 or 

 1842, Dr. J. W. Mighels sent me specimens of one species, 

 under the name of Apella scissura ; but his generic name was 

 never published, and his species, if not identical with any 

 Avhich Mr. Lea afterwards described, seems to have been over- 

 looked and forgotten. 



"On the 14th of December, 1842, Mr. Lea read a j)aper be- 

 fore the American Philosophical Society, in which he de- 

 scribes Melania excisa and Anculosa incisa. In his remarks 

 upon these species he alludes to the pleurotomose cut in the 

 superior part of the upper lip, and at the same time suggests 

 the necessity, in consequence of this character, to construct a 

 new genus, which he proposed to call ' ScMzostoma.'' Mr. Lea 

 finding his name ' Schizostoma,'' pre-occupied in Paleontology, 

 changed it to ' SchizocMlus^ (March 5, 1852, Obs., v., p. 61). 

 In a paper read May 2, 1845, Mr, Lea, in a foot-note to p. 

 93, first indicates the generic characters of Sddzostoma, as 

 follows, — ' Testa vel conica vel fusiformis ; labrum superne 

 fissura; apertura ovata; columella l^vis, incurva,'' — and de- 

 scribes six additional species. 



"In the above concise definition of the genus, it will at once 

 be noted that the fissure at the upper part of the outer lip is 

 after all the essential character ; and Mr. Lea himself seems to 



