1 152 VIRGUS 



it is carried out with a slight curve to the extreme hind end of 

 the shell ; anterior end rounded ; posterior ridge high, nar- 

 rowly rounded, separated above and below from the rest of the 

 shell by a sulcus, the ridge ending behind at the base of the 

 shell ; surface with dense, concentric striae, which are crossed 

 below the posterior ridge with strong, nearly vertical folds ; 

 dorsal slope sculptured with folds ; epidermis olivaceous-fus- 

 cous ; pscudocardinals small, sulcate above, unequally dentate 

 on the margin; laterals elongated; nacre silvery or bluish 

 white. The beaks are tumid and plicate. 



Length 90, height 29, diam. 16 mm. 



Fly River, New Guinea. 

 Unio heccarianus T.\pPERONE-CANEf"Ki, Ann. Mus. Genov., 



XIX, 1883, p. 291, pi. XT, fig. 2. 

 Virgus heccarianus Simpson, Syn., 1900, p. 852. — Haas, Con. 



Cab., Unio, 1910, p. 129, pi. xiii, fig. i. 



.\ greatly elongated shell which is drawn out to a point be- 

 hind at the base. It is remarkable for its high, rounded pos- 

 terior ridge, which is separated from the rest of the surface 

 by distinct sulci and for the vertical plications below it. 



Group of J-'irgiis mattiroli. 



Posterior ridge full, rounded, not outlined by sulci, covered 

 with very strong corrugated ridges, which curve outward each 

 way from the center, the remainder of the shell smooth. 



Virgus mattirou (Tapperone-Canefri). 



Shell somewhat elongated, solid, inequilateral, subinflated; 

 base line nearly straight ; dorsal line parallel with it as far 

 back as the hinder end of the ligament, from that to the pos- 

 terior point it is slopingly truncate ; anterior end rounded ; 

 posterior ridge full, ending in a rounded point at the base of 

 the shell, sculptured throughout its length with very strong, 

 divaricate ridges ; beaks only moderately full ; pscudocardinals 

 two in each valve subcompressed, laterals club-shaped, one in 

 the right valve and two in the left ; nacre bluish-white. 



Length 52, height 26, diam. 15 mm. 



Flv River, New Guinea. 



