PLEUROBRANCHID^. i) 



Family III. PLEUROBRAN'CHID.E, 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 jDresent wholly external or internal, oval or 

 conical: sjoire 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^ Cu\der. PI. 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 ' Annales 

 du Museum d^Histoire Naturelle^ for 1805_, his type 

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

 In ]815 Montagu proposed another generic name^ 

 Lamellaria, which is now applied to mollusca belonging 

 to the Velutina family. In my account of the genus 

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

 was " afterwards " established by Cuvier. Such is the 

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



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



b5 



