PHYSUNIO 1063 



Section Physunio s. s. 

 Shell inflated ; beak cavities deep and rounded. 



Physunio gravidus (Lea). 



Shell irregularly obovate, inflated, thin inequilateral ; beaks 

 full and high, the sculpture apparently almost radial, with two 

 radiating ridges, the hinder one bearing pustules ; posterior 

 ridge often scarcely marked, but faintly angulate, and ending 

 in a slight angle below the median line ; sometimes there are 

 one or two feeble, dark ridges on the dorsal slope ; hinge line 

 slightly sinuous, running up into a low wing, behind which 

 it is almost squarely truncated posteriorly ; anterior end nar- 

 rowed and rounded ; base line almost angularly inflated be- 

 hind the middle; surface with fine, radial or chevron-shaped 

 wrinkles on the dorsal slope ; epidermis ashy-yellowish, green- 

 tinted, sometimes having faint, dark ashy rays, smooth, dull 

 or shining ; left valve with one elongated, compressed, ragged 

 pseudocardinal and two remote, curved laterals ; right valve 

 with two compressed pseudocardinals, the upper small and one 

 lateral ; muscle scars shallow ; nacre brilliant, bluish, silvery 

 and iridescent. 



Length loi, height 81, diam. 60 mm. 



Siam ; Cambodia ; Cochin China. 

 Unio gravidus Lea, Pr, Ac. N. Sci. Phila., V^III, 1856, p. 93 ; 



Obs., VL 1857, p. 12, pi. XXIV, fig. 5 ; Jl. Ac. N. Sci. Phila., 



in, 1858, p. 292, pi. XXIV, fig. 5. — SowERBY, Conch. Icon., 



XVI, t8(56, pi. Lii, fig. 271. 

 Margaron fUnio) gravidus Lea, Syn., 1870, p. 28. 

 Lampsilis gravidus Rochebrune, Bull. Soc. Phil., VI, 1882, 



P- 43- 

 Physunio gravidus Simpson^ Syn., 1900, p. 830. — ^Haas, Conch. 



Cab., Unio, 1912, pi. 35, fig. i. 

 Unio abnormis Morelet, Rev. et Mag., XIV, 1862, p. 480. 

 Unio superhus Sowerby, Conch. Icon., XVI, 1867, p. LIX, 



fig- 295- 



A magnificent shell of delicate structure and large propor- 

 tions, the nacre being of a remarkable shade of blue, silvery 



