50 ONCHIDIAD^. 



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- 

 culidcB and LimniadcB. 



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 ; jaAVS none ; teeth numerous, four-sided, 

 flat, close together, side by side * ; shell none. 

 Fluviatile, or marine. 



Fam. 1. ONCHIDIADiE. 



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. SoeAim. and 

 Mag. N. H., Jan. 1854. 



