PLEUROBRANCHID/E. 9 



Family III. PLEUROBRAN'CHIME, Forbes 



and Hanley. 



Body tortoise-shaped or semioval, fleshy: mantle enveloping 

 the upper part of the body, and forming a veil in front : head 

 proboscidiform, retractile, not prominent, but partly concealed 

 by the pallial veil : tentacles 2, close together, folded so as to 

 appear tubular and slit down the middle : eyes sessile, at the 

 base of the tentacles.: foot large, expanded at the sides: gills 

 composing a long plume with a double row of leaflets ; it is 

 free towards the point, and more or less protruded ; its stalk 

 is attached between the junction of the mouth and foot on the 

 right-hand side. Sexes united, the organs of generation being 

 nearly contiguous. 



Shell when present wholly external or internal, oval or 

 conical: spire visible, minute, dextrorsal: mouth very large 

 and open. 



A small but peculiar family, and widely distributed. 

 It was included by Lamarck in his ' Phyllidiens/ along 

 with Chiton and Patella. 



Genus PLEUROBRANCHUS* Cuvier. PL I. f. 2. 



Body more or less depressed. 



Shell internal, oval or ear- shaped : spire nearly terminal. 



This genus was founded by Cuvier in the ' Aimales 

 du Museum d'Histoire Naturelle' for 1805, his type 

 being P. Peronii, an inhabitant of the Indian Ocean. 

 In 1815 Montagu proposed another generic name, 

 Lamellaria, which is now applied to mollusca belonging 

 to the Velutina family. In my account of the genns 

 Lamellaria (vol. iv. p. 234) I stated that Pleurobranchus 

 was l ' afterwards " established by Cuvier. Such is the 

 case with regard to the date of publication of his cele- 



* From its gills or branchiae being placed at the sides. 



b5 



