322 MAJftriL OF THE MOLLrSCA. 



Animal shell-less, ornamented ■with filaments, sometimes 

 dendritic, foot narrow, lateral crests united, leaving only a 

 narrow branchial slit ; gills not covered by an opercular mantle 

 lobe. 



Distribution, 7 species. Mediterranean, Eed Sea. 



ICABTJS, Forbes, 1843. 



Type^ I. Gravesii, F. 



Synonym, Lophocercus (Sieboldtii) Krohn, 1847. 



Shell like BuUeea ; convoluted, thin, ovate, covered with 

 epidermis, outer lip separated at the suture, posterior angle 

 inflected and rounded. 



Animal slender, papillose; tentacles 2, ear-shaped; eyes 

 sessile on sides of head ; side-lobes reflected and partly covering 

 the shell, united behind ; tail long and pointed. 



LoBiGER, Krohn. 



Type, L. Philippii, PL XIV., Fig. 16. Sicily. 



Shell oval, transparent, flexible, slightly convoluted ; covered 

 with epidermis. 



Animal slender, papillose, with two flattened, oval tentacles, 

 and minute sessile eyes on the sides of the head ; shell exposed 

 on the middle of the back, covering the plume -like gill ; sides 

 with two pairs of rounded, dilated lobes, or natatory appendages, 

 foot linear, tail long and slender. 



Distribution, 4: si^eciea. Atlantic; South Europe. 



Family IV. — pLEtJROBKAircHrDJE. 



Shell limpet-like or concealed, rarely wanting ; mantle or 

 shell covering the back of the animal ; gill lateral, between the 

 mantle-margin and foot ; food vegetable, stomach extremely 

 complicated. 



Pleurobranchits, Cuvier. 



Example, P. membranaceus, PL XIV. , Fig. 17. 



Etymology, pleura, side, branchia, gill. 



Synonyms, Berthella (plumula), BL Oscanius (membr.), G-rf y. 



Shell internal, large, oblong, flexible, slightly convex, 

 lamellar, with a posterior, sub-spiral nucleus. 



Animal oblong, convex ; mantle covering the back and sides, 

 papillated, containing spicula; foot large, separated from the 

 mantle by a groove ; gill single, free at the end, placed on the 

 right side between the mantle and foot ; orifices near the 



