50 ONCHIDIADJE. 



III. LIMNOPHILA. Eyes sessile ; tentacles two, 

 subcylindrical, 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- 

 culidce and Limniados. 



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. PETROPHILA. 



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. 

 Fluviatile, or marine. 



Fam. 1. ONCHIDIAD^E. 



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. 



