48 INTRODUCTION. 



As, for reasons which may be gathered from the pre- 

 ceding remarks, the genera and species of the pneumo- 

 brancliiate mollusks proposed by M. Rafinesque, are 

 considered to be destitute of authority, and entirely 

 imworthy of notice, no mention will be made of them 

 in the text. But, to sliield the author from a charge, 

 from any quarter, of having designedly suppressed them, 

 a brief account of all of them known to him, is here 

 added. In a memoir published in the Journal de Phy- 

 sique, Paris, June, 1819, M. Rafinesque proposed no 

 less than seventy new genera of North American ani- 

 mals, among which eight were formed out of the genus 

 HelLx. These are founded, upon only slight variations 

 of the aperture of the shell, and so similar are some of 

 them to each other, that where he saw reasons to create 

 generic distinctions, others, at the present day, can see 

 only such diflFerences as belong to varieties of species. 

 The genera proposed by him at that time, were the 

 followmg : — 



Odotropis. " Lip reflected, umbilicus covered, tooth upon 

 columella. 



it is a positive fact, that in knowledge I have been a Botani-st, Natnrahst, 

 Geologist, Geographer, Historian, Poet, Pliilosopher, Philologist, Economist, 

 Pliilanthropist. — By profession a Traveller, Merchant, Manufacturer, Col- 

 lector, Improver, Professor, Teacher, Lawyer, Draftsman, Architect, En- 

 gineer, Pulnaist, Author, Editor, Bookseller, Librarian, Secretary, . . . and 

 I hardly know myself what I may not become as yet ; siiice whenever I 

 apply myself to anything ivJdch lUle, I never fail to succeed if depending 

 on me alone, unless impeded and prevented by lack of means, or tlie hos- 

 tility of the foes of manlcind."' 



