GASTEROPODA. 187 



FAMILY IV. Pleurobranchid^. 

 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. 



Pleurobranchus, Cuvier. 



Ex. P. membranaceus, PI. XIV. fig. 17. Etym. Pleura side, hranchia ^\\\. 



Si/n. BertheUa (plumula) Bl. Oscanius (membr.) Gray. 



Shell internal, large, oblong, flexible, slightly convex, lamellar, with a 

 posterior, subspiral 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 base of the gill ; head with 2 grooved tentacles, eyes at their 

 outer bases ; mouth armed with horny jaws and covered by a broad veil with 

 tentacular lobes. 



Distr. 20 sp. S. America, Norway, Brit. Medit. Red Sea. 



Sub-genus ? Fleurohranchcea Meckel; P. Meckelii, Leve, Medit. Syn. 

 Pleurobranchidium (maculatura), Quoy, S. Australia. Mantle-margin very 

 narrow, not concealing the giU; dorsal tentacles eai-like, oral veil tentaculi- 

 form. 



PosTEROBRANCH^A, D'Orbigny. 



Type, P. maculata, D'Orb. Coast of Chile. 



Animal shell-less ; oval, depressed, covered by a mantle broader than the 

 foot ; foot oblong, bi-lobed behind ; branchial plume on the left side, pro- 

 jecting posteriorly ; reproductive orifice in front of giU, excretory behind ; 

 proboscis covered by a broad bi-lobed veil ; no dorsal tentacles. 



RuNCiNA, (Forbes) Hancock. 

 Type, R. Hancocki, Forbes. Syn, ? Pelta, Quatr. (not Beck.) 

 AnimalmiXMit, slug-like, with a distinct mantle; eyes sessile on the front 

 part of the mantle ; no tentacles ; gills 3, slightly plumose, placed with the 

 vent on the right side, at the hinder part of the back, beneath the mantle ; 

 gizzard armed ; reproductive organs on the right side. 

 Bistr. on Confervce near high-water mark, Torbay. 



Umbrella, Chemnitz. Chinese -umbrella shell. 



Type, U. umbellata, PI. XIV. fig. 18. Syn. Acardo, Lam. Gastroplax, Bl. 



Shell Hmpet-like, orbicular, depressed, marked by concentric lines of 

 growth ; apex sub-central, oblique, scarcely raised ; margins acute ; inner 

 surface with a central coloured and striated disk, surrounded by a continuous 

 irregular muscular impression. 



Animal with a very large tuberculated foot, deeply notched in front ; 

 mouth small, proboscidiform, retractile into the pedal notch, covered by a 



