CONCHIFEEA. 435 



lEiDmA, Lamarck. 



Synonyms, Mutela, Scop. Spatha, Lea (including Mycetojpus), 

 Leila, Gray. 



Type, I. exotioa, PI. XYIII., Fig. 5. 



Etymology f iris, tho rainbow. 



Shell oblong ; umbones depressed ; hinge-line long, straight, 

 attenuated towards the umbones, crenated by numerous unequal 

 teeth ; ligament long and nexro"W. 



Animal with mantle-lobes united posteriorly, forming two 

 short siphons ; mouth and lips small ; p.alpi immense, oval ; gills 

 united to the body. 



Iridina ovaia (Pleiodon, Conrad) has a broader hinge-line. 



Distribution^ 9 species. Eiyers of Africa, Nile, Senegal. 



Mycetopus, D'Orbigny. 



Etymology, muJces, a mushroom, pons, the foot. 



Type, M. soleniformis, PI. XYIII. , Fig. 6. 



Shell elongated, sub-cylindrical, gaping in front ; margins 

 sub-parallel, hinge edentulous. 



Animal with an elongated, cylindrical foot, expanded into a 

 disk at the end ; mantle open ; gills equal ; palpi short. 



Distribution, 3 species. Eiyer Parana, Corrientes ; River 

 Amazon, Bolivia. 



-2ETHEEIA, Lamarck. 



Type, M. se^nilunata, PI. XYIII., Pig. Y. {Aitherios, aerial.) 



Shell irregular, inequivalve ; attached by the umbo, and 

 tubular processes of one of the valves, usually the left ; epidermis 

 thick, olive ; interior pearly, blistered (as if with air-bubbles) ; 

 hinge edentulous ; ligament external, with a conspicuous area 

 and groove in the fixed valve ; two adductor impressions, the 

 anterior very long and irregular ; pallial line simple. 



Animal with the mantle-lobes open ; body large, oblong, pro- 

 jecting backwards ; no trace of a foot ; palpi large, semi-oval ; 

 gills sub-equal, plaited, united posteriorly, and to the body and 

 mantle. 



Distrihution, 4 species. River Nile, from first cataracts to 

 Fazool ;* Biyer Senegal. 



MuLLERiA, Ferussac. 



Dedicated to Otto Frid. Miiller, author of the " Zoologia 

 Danica." 



Type, M, lobata. Per., Fig. 222, 



Syruonym, Acostsea (Guaduasana), D'Orbigny. 



• The " fresh-water oysters " discovered by Bruo*, 

 U 2 



