244 ^theriiDjE. 



Mycetopus, d'Orbigny, 1835. 



Etym. — Mukes^ a mushroom ; poiis^ the foot. 



Distr. — 3 sp. River Parana, Corrientes ; River Amazon, 

 Bolivia. M. soleniformis^ Orb. (cxxv, 11). 



Shell elongated, subcylindrical, 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. 



SOLENAIA, Conrad. Elongated, thin, gaping anteriorly, hinge 

 with a long, acicular lateral tooth in each valve, slightly 

 developed. Recent ; Oriental. M. emarginatus, Lea (cxxv, 

 12, 13). 



(jEtheriacea.) 



Family iETHERIID^. 



Shell irregular, inequivalve, attached, pearly within. Animal 

 without foot. These may be likened to oysters, which they 

 much resemble in the general appearance of the shell. The 

 family includes three somewhat similar genera, one of which is 

 African, the others South American. 



^THERiA, Lamarck, 1808. 



Etym. — Aiiherios, aerial. Fresh-water oyster. 



Distr. — 4 sp. River Nile, from first cataracts to Fazool ; River 

 Senegal. ^. Gailliaudi^ Fer. (cxxiv, 6). 



Shell ii-regular, 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, semioval ; 

 gills subequal, plaited, united posteriorly^, and to the body and 

 mantle. 



MuLLERiA, Ferussac, 1823. 



Etym. — DedicatedtoOttoFrid. Miiller, author of the" Zoologia 

 Danica." Syn. — Acostaa, d'Orbigny, 1851. 



Distr. — River Magdalena, near Bogota, New Grenada. 3L 

 Guaduasiana^ Orb. (cxxv, 14, 15). ' 



Shell, when young, free, equivalve, Anodon-shaped, with a 

 long and prominent ligament, and two adductor impressions ; 

 adult irregular, inequivalve, attached by the right valve ; umbones 

 elongated, progressively filled up with shell, and forming an 

 irregular " talon " in front of the fixed valve ; epidermis thick ; 

 ligament in a marginal groove ; interior pearly, muscular impres- 

 sions single, posterior. 



