TEBENNOPHORUS 1 9 



GEOGRAPHICAL DISTRIBUTION. This genus occurs in 

 every part of the country from the Gulf of Mexico to 

 Lake Erie, except the tertiary section of the extreme 

 south, where it has not yet been noticed. 



REMARKS. The species on which this genus is found- 

 ed is lAmax Caroliniensis of Bosc. M. Ferussac included 

 it in Rafinesque's genus PTdlomycus, which is distin- 

 guished from lAmax by the absence of the mantle. 

 Having adopted Rafinesque's genus with all its char- 

 acters, he nevertheless, by a singular inconsistency or 

 oversight, arranged it under that division of the family 

 containing the species entirely covered with a mantle. 

 It thus found a position more in accordance with its real 

 characters than it would have done, if the generic defi- 

 nition of M. Rafinesque or the description of M. Bosc 

 had been kept in mind. The editors of the new edition 

 of M. Lamarck's work have again, more recently, de- 

 scribed it as destitute of a mantle, but in truth it pos- 

 sesses a well characterized mantle, detached from the 

 body at its anterior part, and around its whole margin. 

 M. Ferussac, supposing the other genera included in the 

 same division to possess only contractile tentacles, by a 

 convenient method of generalization, inferred, that this 

 species also was destitute of the power of retracting these 

 organs ; we know very well, however, that they are 

 retracted by inversion, hi the same manner as those of 

 the Limaces and Helicidce. He speculated also upon 

 the uses of the development of the structure of the 



