INTRODUCTION. 53 
decurrent on the whorl obliquely and with a very small 
umbilicus. The name means half margin. 
" Hcmiloma ovata. Ovate, very obtuse, smooth, six spires, 
breadth two thirds of the length. Found near Lexington 
in a nearly fossil state ; whitish, length three sixteenths of 
an inch. 
In the same paper lie also describes a species of 
Limax, viz. : 
" Limax gracilis. Body slender, head and lower tentacula 
fulvous, neck gray, upper tentacula brownish, mantle dark 
fulvous, back smooth brown, beneath dirty white ; tail brown, 
obtuse above, mucronate and acute beneath ; probably a real 
Limax. Yet it has the two long tentacula inserted above the 
neck, while the small ones are terminal and all slightly club- 
shaped. It may, perhaps, form a sub-genus Deroceras. 
Length over one inch. Kentucky, in the woods. 
The shell upon which the genus Heroiloma was found- 
ed has not been recognized ; it was probably a fossil. 
There is reason to believe, that Philoniycus and Eumelus 
originated in the defective and careless observation of 
M. Rafmesque. Certain it is, that no other observer 
has yet found naked slugs with the four tentacles in one 
row and nearly equal, with the two long ones inserted 
above the neck, or without a more or less developed 
mantle. A hasty examination of small individuals of 
the animal, which in this work is included in a genus for 
which the author has proposed the name of Tebennopho- 
rus, might readily deceive any one who did not suspect 
their peculiar characteristics, as the mantle is often so 
VOL. I. 15 
