16 PLEUROPHYLLIDIID.'E. 



Specimens wliich Mr. Thompson kindly sent me from 

 Weymouth in a bottle of sea- water with Confervse;, were 

 dark purplish-brown with minute round spots of yellow 

 and a streak of the former colour on the tail ; the sides 

 of the front portion of the mantle,, as well as the hinder 

 portion and the sides of the tail, were buff; the eyes 

 were indistinct, deeply sunk in the outer skin, and not 

 encircled by rings; the mouth was furnished with a 

 pair of large triangular lips or lobes; the branchial 

 plumes lay on the right-hand side of the vent, which 

 was placed in the middle of the hinder edge of the 

 mantle ; and the whole substance of the body was 

 parenchymatous. They were extensile and exceedingly 

 active. The figures given by Messrs. Adams and those 

 in the ' British Mollusca ^ are not satisfactory. The dis- 

 coverers of this singular little moUusk suspected that 

 Pelta of Quatrefages may be the young before the 

 branchial apparatus is developed. If that be the case, 

 why was Runcina substituted for the older name ? 



Family V. PLEUROPHYLLIDriD^, 



H. & A. Adams. 



Body oblong, depressed, fleshy : mantle of a somewhat 

 coriaceous textiu'e, covering the upper part of the body and 

 notched in front : head short, broad, and forming a triangular 

 lobe in front of the mantle ; it is mostly furnished with plaited 

 lips and a pair of veiy strong hornyjaws : odontophore broad ; 

 teeth numerous, arranged in cross rows : tentacles 2, very 

 small, conical or club-shaped, close together, retractile, each 

 in a socket within the pallial notch : foot elongated, somewhat 

 narrower than the mantle, shghtly indented in front and 

 abruptly pointed behind : gills placed under the edges of the 

 mantle on the hinder two- thirds of the body, and aiTanged in 



