1064 riivs-UNio 



and almost as rich as that of a Nauitiiiis. The greatest diame- 

 ter is just behind the beaks ; from this point there is a sudden 

 and regfular decrease in diameter to either end. The species 

 is closely allied to P. supcrbus but is not quite so solid, is less 

 inflated, is lighter colored and has a more brilliant nacre. 



PiiYSUNio supiCRBUS (Lea). 



Shell large, irregularly obovate, somewhat inflated, inequi- 

 lateral, scarcely subsolid ; beaks full and high, their sculpture 

 apparently zigzag- radial, and having a row of tubercles on 

 their posterior ridge; hinge line lightly curved, with a small 

 wing behind ; anterior end narrowed and rounded, angled 

 above; base line almost straight but very full behind the mid- 

 dle ; posterior end almost squarely subtruncate ; posterior ridge 

 moderate, lightly angled, ending in a rounded point below the 

 median line ; surface with irregular, concentric growth lines ; 

 epidermis smoky-brown or smoky-olive, scarcely shining; 

 pseudocardinals elongated, ragged, one in the left valve and 

 two in the right ; laterals remote, curved, two in the left valve 

 and one in the right ; muscle scars shallow ; nacre bluish-white^ 

 smoky-tinted, iridescent behind. 



Length 93, height 75, diam. 44 mm. 



Sumatra ; Cochin China. 

 Unio superhus Lka, Desc. 12 New Uniones, 1843 ("o pagina- 

 tion) ; Tr. Am. Phil. Soc, IX, 1845, P- 281, pi. xlii, fig. 11 ; 



Obs., JV, 1848, p. 39, pi. xui, fig. II. 

 Margaron (Unio) sitperbus h^A, Syn., 1852, p. 19; 1870, p. 28. 

 Physunio superhus Simpson, Syn., 1900, p. 830. — Haas, 



Conch. Cab., Unio, 1912, pi. 35, fig. 2. 

 Unio I'elaris Hajv[le;y, Biv. Shells, 1856. p. 385, pi. xxiii, fig. 



42. 

 Unio massini Morelet, Jl. de Conch., XU, 1864, p. 288; Ser. 



Conch.. TV, 1875. p. 348, pi. XV, figs. i. 3. 



A fine species, close to graz'idus but solider. having a darker 

 epidermis, less inflated, v/ith a curved hinge line instead of a 

 sinuous one. and with smoky-bluish nacre, not nearly so bril- 

 liant ,ns that of groridus. There are one or two darker rays on 

 the posterior slope. 



