10. 



Plate I. 



Genus 10, Lea. 



Testa fusiformis, solidiuscula, plerumqne purpureo-fasciata, 

 epidermide olivaced induta, anfractibus declivibus, ad 

 peripheriam gibbosis et scepissime iuberculatis aid no- 

 daiis; columella plus minus tenuiter prolongatd et 

 contorta, aperturd bad sinuatd vel canaliculate!. 

 Shell fusiform, rather solid, generally purple-banded, co- 

 vered with an olive epidermis, whorls sloping, gib- 

 bous, and mostly tubercled or noduled at the peri- 

 phery ; columella more or less thinly prolonged and 

 twisted, aperture either siuuated or channelled at the 

 base. 

 The very elegant fusiform convolution of the type of 

 this genus, Io spinosa, is not unworthy of the beautiful 

 priestess after whom it is named, but the fabled story of 

 her wanderings on the banks of the Nile is not indicative 

 of the habitat of the genus. With one single exception, 

 I.pagodula, from Siam, the genus is purely American, and 

 the typical species are all natives of rivers in the western 

 State of Tennessee. 



The genus Io is founded mainly on the character of the 

 fusiform prolongation of the columella, by which the aper- 

 ture is more or less channelled ; and associated with these 

 are a few intermediate forms, little more than sinuated, 

 which pass into both Anculotus and the Ceriphasia divi- 

 sion of Melania. In all the species the whorls slope to a 

 more or less gibbous circumference at the periphery, which 

 is either noduled or stoutly tuberculed. In the Siamese 

 species the tubercles are replaced by open prickly scales, 

 and, although claiming unquestionably a place in the 

 genus, it has a very distinct typical character in specific 

 detail. 



Species 1. (Mus. Cuming.) 



Io spikostoma. Io testa obeso-fusiformi, solidd, flaves- 

 cente-olivaced, obscure purpureo-fasciata, anfractibus 

 sex, concavo-declivibus, ad peripheriam subobtuse spi- 

 noso-tuberculatis ; columella spin/liter contortd. 



The sfiral-mouth Io. Shell stoutly fusiform, solid, 

 yellowish-olive, obscurely purple-banded, whorls six, 

 concavely sloping, rather bluntly spine-tubercled at 

 the periphery ; columella spirally twisted. 



Anthony, MS. in Mus. Cuming. 



Hab. Tennessee, United States. 



Of rather obtuse growth, characterized by the canali- 



culated extremity of the columella being twisted into a 

 distorted spiral. 



Species 2. (Mus. Cuming.) 

 Io verrucosa. Io testa ftisiformi, virescenle-olivaced, 

 purpureo tinctd et fasciatd, anfractibus sex, declivibus, 

 primis plicato-crenatis, ceeteris ad peripheriam tumido- 

 nodatis ; columella atteuualo-elougatd. 

 The warty Io. Shell fusiform, greenish-olive, purple- 

 tinged and banded, whorls six, sloping, the first pli- 

 cately crenulated, the rest tumidly noduled at the 

 periphery ; columella attenuate!)' elongated. 

 Hab. Tennessee, United States. 



In this species, which is of a greenish hue, the peri- 

 phery of the whorls is furnished with a row of swollen 

 wart-like nodules, the early whorls of the shell being 

 rippled with small concentric folds. 



Species 3. (Mus. Cuming.) 

 Io tenebkosa. Io testa fusiformi, olivaced, purpureo 

 conspicue fasciatd, anfractibus sex, concavo-declivibus, 

 ad peripheriam tumidis, et vix obsolete nodatis ; co- 

 lumella attenuato-elongatd, subcontortd. 

 The dark Io. Shell fusiform, olive, conspicuously 

 purple-banded, whorls six, concavely sloping, swollen 

 and scarcely obsoletely noduled at the periphery; 

 columella attenuately elongated, somewhat twisted. 

 Lea, Trans. Amer. Phil. Soc. v. 

 Hab. Tennessee, United States. 



The periphery of the whorls in this species is distin- 

 guished by a swollen gouty appearance, and the shell is 

 convoluted in a somewhat bent manner. 



Species 4. (Mus. Cuming.) 



Io brevis. Io testa obeso-fusiformi, solidd, flavescente- 

 olivaced, purpureo fasciatd, anfractibus sex, concavo- 

 declivibus, ad peripheriam valide spinoso-tuberculalis ; 

 columella abbreviato-conlorld, appressd, canali late 

 effuso. 



The short To. Shell stoutly fusiform, solid, yellowish- 

 olive, purple-banded, whorls six, concavely sloping, 



April, 1860. 



