CONCniFEEA. 435 



Iridina, Lamarck. 



Synonyms^ Mutela, Scop. Spatha, Lea (including Mycetopus). 

 Leila, Gray. 



Type, I. exotioa, PL XVIIL, Fig. 5. 



Etymology, iris, the rainbow. 



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

 attenuated towards the umbones, crenated by numerous unequal 

 teeth ; ligament long and narrow. 



Animal with mantle-lobes united posteriorly, forming two 

 short siphons; mouth and lips small; palpi immense, oval ; gills 

 united to the body. 



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



Distribution, 9 species. Eivers of Africa, Nile, Senegal. 



Mycetopus, D'Orbigny. 



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



Type, M. soleniformis, PI. XVIIL, 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. Eiver Parana, Corrientes ; Eiver 

 Amazon, Bolivia. 



^THEEIA, Lamarck. 



Type, M. semilunata, PL XVIIL, Fig. 7. {Aitherios, atrial.) 



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. 



Distribution, 4 species. Eiver Nile, from first cataracts to 

 Fazool ; * Eiver Senegal. 



MuLLERiA, Ferussac. 



Dedicated to Otto Frid. Miiller, author of the ' * Zoologia 

 Danica." 



Type, M. lobata, Fer., Fig. 222. 



Synonym, Acostsea (Guaduasana), D'Orbigny. 



* The " fresh-water oysters " discovered by Bruce. 

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