161 



them from the species I have regarded as decisa and Integra, which are 

 abundant here. The shell of P. rufa may be called ovate conic, while 

 the shells of decisa (f) and integra (?) are conic. This results from 

 the greater angular divergence of the apical whorls of rufa, and 

 the subsequent diminution of the angle of the body whorl. The angle 

 for decisa (?) and integra (?) is constant in each, for all the whorls. 

 The interior of rufa is colored pink, which in some specimens deepens 

 to a faint purple, and also by reflection through the epidermis imparts 

 a faint purple tinge to the exterior of the shell. The apical whorls 

 are pink (externally), and contrast with the ohvaceous hue of the 

 larger whorls. In integra (?) and decisa (?) the apices are not col- 

 ored, and if any contrast is shown with the larger whorls, it is due to 

 a want of coloring matter in the apical whorls. 



[There is some doubt about the identification of the shells of decisa 

 and integra, and they may not be, and probably are not, the shells de- 

 scribed by Mr. Say, though they are unquestionably the shells alluded 

 to by DeKay.] 



Melania virginica Gmel. was also first observed in the same 

 portion of the canal where Pal. rufa was discovered. It has since 

 been detected in other portions of the canal in somewhat greater 

 nimibers, but it yet remains a rare shell. This and Pal. rufa have, 

 no doubt, been introduced from other portions of the State, on the 

 bottoms of boats. Both species are found at the Eastern and West- 

 ern terminus of the canal. 



Melania ? isoGONA Say, is a very recently-introduced species, 

 the first and only specimens yet found having been taken within the 

 last four weeks. They are probably introduced from Buffalo, at 

 which point they have been detected by Mr. C. T. Robinson, of that 

 city. 



The few specimens I have been able to secure here enable me to 

 correct an error in the generic nomenclature of this species. Mr. 

 Say first noticed it as a Melania. It has since been catalogued by 

 the Smithsonian Institute as an Anculosa (Leptoxis Eaf). The 

 form of the shell suggests, however, different relations, and the soft 

 parts confirm the suggestion that the animal belongs to the genus 

 Amnicola, Hald. and Gould. 



[I enclose herewith an enlarged sketch of the foot of the animal, 

 as seen from below, through the side of a glass vessel, in which the 

 animal was crawling. Foot white and translucent, with a recurved 

 projecting angle on each side in front, widening a little posteriorly, 

 and terminating in a slightly emarginate semicircle of a radius equal 

 to one-half the width of the foot. Tentacles white, filiform, nearly 

 straight, and of nearly equal diameter throughout ; length of tenta- 



PROCEEDINGS B. S. N. H. — VOL. IX. 11 FEBEUAKT, 1863. 



