NATURAL SCIENCES OF PHILADELPHIA. 63 



Obs. A peculiarly slender, graceful species, in form somewhat like 31. strigosa, 

 Lea, but more folded and more slender. The striae on the upper whorls are 

 very distinct where they intersect the folds, and give the shell a tuberculous 

 appearance ; the folds are arrested by the carina, which is elevated. The brown 

 lines on the body whorl are often slightly elevated, but nevertheless, indistinct, 

 and are about four in number. A faint line or band of a yellow color revolves 

 around the upper portion of the two lower whorls. 



Gyrotoma. 



As some confusion exists regarding the name of this genus, the following 

 notes are given : 



The genus Melatoma was established by Swainson, and first given to the 

 world in 1840, in his "Treatise on Shells and Shell Fishes," published in 

 London, founded, as he says, (p. 202,) " upon a remarkable Ohio shell sent 

 him many years before by his old friend Prof. Rafinesque." "It has," he 

 remarks, " the general form of a Pleurotoma and of a Melafusus, 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 pleuro- 

 toma-like cut in the outer lip as applied to a fluviatile univalve is altogether 

 sufficient to indicate the 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, exclusively 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. and 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 authors, 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 which Mr. 

 Lea afterwards described, seems to have been overlooked and forgotten. 



On the 14th of December, 1842, Mr. Lea read a paper before the American 

 Philosophical Society, in which he describes 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 possibility of 

 its being necessary, in consequence of that character, to construct a new genus, 

 which he proposed to call " Schizostoma." Mr. Lea finding his name " Schizos- 

 toma" preoccupied in Palaeontology, changed it to " Schizochilus." (March 5, 

 1852, Obs. v. p. 51.) In a paper read May 2d, 1845, Mr. Lea, in a foot-note to 

 page 93, first indicates the generic characters of Schizostoma as follows : 

 "Testa vel conica vel fusiformis ; labrum superne fissura; apertura ovata; 

 columella lsevis, incurva;" and describes 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 be aware of this, since of the six species then described 

 he states the aperture to be elliptical in five cases and rhomboidal in the other, 

 although his generic character is "aperture ovate;" indeed in the species 

 described by him but a single one has the aperture ovate, and that one is 

 described as an Anculosa. 



I860.] 



