285 
5. Physunia eximius Lea. 
Taf. 34. fig. 6—8. 
IJnio eximius Lea, ProG. Acad. Nat. Sciences, Philadelphia, Vol. 8, 1856, p. 93; Observations 
Vol. 6, 1857, p. 14, Taf. 25, fig. 8; Journ. Acad. Nat. Sciences, Phila- 
delphia, Vol. 3, 1858, p. 294, Taf. 25, fig. 8. — v. Martens, Proc. Zool. 
Soc. London, 1860, p. 15. — Sowerby in: Eeeve, Conch. Iconica, Vol. 
16, 1868, Taf. 89, fig. 481. — Paetel, Katalog Conch. Samml., Vol. 3, 
1900, p. 152. — P, Fischer, Bull. Soc. hist. nat. Antun, Vol. 4, 1891 
p. 224. — H. Fischer & Dautzenberg, Mission Pavie Indochine, Vol. 3, 
1904, p. 438. 
Margaron (Unio) eximins Lea, Synopsis, 1870, p. 28. 
Physunio eximius Simpson, Synopsis, 1900, p. 831. 
Unio semiquadrata Sowerby in Reeve, Conch. Iconica, Vol, 16, 1866, Taf. 47, fig. 258. 
Unio semiquadratus Paetel, Katalog Conch. Samml., Vol. 3, 1890, p. 167. — P. Fischer, 
Bull. soc. hist. nat. Antun, Vol. 4, 1891, p. 139. 
Testa alata, plicata, obovata, compressa, valde inaequilaterali, postice rotundata; val- 
vulis tenuissimis; natibus prominulis; epidermide virido-lutea, obsolete radiata ; dentibus car- 
dinalibus lamellatis tenuibusque ; lateralibus longis, lamellatis subcurvisque ; margarita cae- 
ruleo-alba et iridescente. 
Shell winged, with numerous small folds over the beaks and posterior slope, obovate 
compressed, very inequilateral, rounded and compressed behind; substance of the shell very 
thin and delicate; beaks slightly prominent and minutely undulate; ligament long and very 
thin; epidermis greenish yellow with three very distinct rays over the posterior slope; car- 
dinal teeth lamellar, double in the right and single in the left valve; lateral teeth long^ 
lamellar and slightly curved, treble in the left and double in the right valve; anterior 
cicatrices confluent and slightly impressed; posterior cicatrices apparently none; dorsal cica- 
trices placed in the centre of the beaks; cavity of the shell very shallow; cavity of the 
beaks shallow angular; nacre bluish white and iridescent. 
Diam. 0,5, Length 1,6, Breadth 2 inches. 
Hab. — Siam. S. R. House, M. D. 
Lea. 
Muschel unregelmässig eiförmig, ungleichseitig, vorn sehr kurz und niedrig, hinten ver- 
längert und hoch, mehr oder weniger schief abgestutzt, ziemlich aufgeblasen und dünn- 
schalig. Vorderer Oberrand geradlinig oder etwas ausgehöhlt, abschüssig, in deutlicher Ecke 
an den steil abfallenden Vorderrand anstossend. Unterrand nach hinten abfallend, etwa in 
der Länge gerundet winklig geknickt, wobei der Scheitel des Winkels den tiefsten 
