50 
ONCHIDIAD^. 
III. Limnophila. — Eyes sessile ; tentacles two, 
siibcylindrlcal, or depressed, simply contractile ; 
jaws two, or three, distinct; teeth numerous, 
flat, with a recurved tip ; orifices of generation 
separate, but near ; operculum none, as Auri~ 
culidcB and LimniadcE, 
IV. Thalassophila. — Eyes sessile, on the back of 
the frontal disk, formed of the united expanded 
tentacles; jaws distinct; teeth numerous, flat, 
close, side by side; operculum none, or distinct. 
Marine. 
Sub-order I. Petbophila. 
Eyes at the end of an elongated contractile pe- 
duncle ; tentacles flat, contractile ; organs of gene- 
ration far apart, apertures united by a lateral 
groove ; jaws none ; teeth numerous, four-sided, 
flat, close together, side by side^; shell none. 
Eluviatile, or marine. 
Earn. 1. ONCHIDIAD^. 
Body ovate or oblong, mantle, covering the whole of 
the back, edging the foot, convex, more or less 
tubercular; tentacles and eye peduncles con- 
tractile; aperture of respiration on the hinder 
* The teeth described as those of Peronia Mauritiana in the 
Annal. and Mag. of Nat. Hist.., Nov. 1853, were those of Testa- 
cellus., which had been sent to me wrongly named. See Ann, and 
Mag. N.H., Jan. 1854. 
