557 



PLEUROBRANCHIDiE. 



This family forms a connecting link between the last 

 two and the nudibranchous groups. The structure of the 

 head and tentacula reminds us of Apli/sia, from which type 

 and its immediate allies it is distinguished, among other 

 features, by the circumstance that the dorsal shield is not 

 a covering or lid for the branchial plume, but a protecting 

 plate for the viscera of the body. 



PLEUROBRANCHUS. Cuvier. 



Shell an internal membranaceous, oblong or suborbicular, 

 expanded shield, with a subspiral apex, lodged in the 

 dorsal region of the mantle. 



Animal oblong or suborbicular, fleshy. Head with two 

 grooved tentacula, the eyes at their external bases ; a 

 broad tentaculiform buccal veil ; mouth provided with cor- 

 neous jaws, and an armed lingual ribband. Branchial 

 plume single, free towards its extremity, placed on the 

 right side between the mantle and foot, the genital organs 

 near its origin, the vent not far from its termination. 

 Foot ample, separated from the mantle by a deep groove. 



The animals of this genus are but poorly represented 

 in the British seas. On the shores of warmer climates 

 they become more plentiful, and are remarkable for the 

 delicate, and often vivid, hues of their bodies. Whoever 

 observes them should make a coloured drawing of their 

 appearance when alive. 



