VI ROUS I 151 



back as the hinder end of the ligament parallel with the base, 

 behind the ligament the shell is obliquely truncate, the trun- 

 cation somewhat upcurved, the shell ending in a rounded 

 point at the posterior base ; posterior ridge elevated, rounded, 

 with sculpture radiating from it above and below ; beaks rather 

 low, radially ridged ; pseudocardinals small, two in each valve ; 

 laterals rather short, club-shaped, one in the right and two in 

 the left valve. 



Animal unknown. 



Under this generic name I have placed three species from 

 New Guinea and Borneo, which agree quite well in general 

 conchological characters. The shells are quite elongated, the 

 dorsal and ventral outlines nearly parallel to the hinder part 

 of the ligament. The ventral line is nearly straight through- 

 out ; the dorsal slope is cut away above in a long oblique trun- 

 cation or subtruncation to a blunt point near the base of the 

 shell. The beaks are low and, no doubt, subradially sculp- 

 tured : the pseudocardinals are short and rather strong; the 

 laterals club-shaped. The group differs from Rectidcns in 

 having solider shells, and strong, short pseudocardinals as well 

 as heavier laterals. 



Key to species oe Vikgus. 



Posterior ridge rounded, separated from the rest of the 



shell by sulci, V. beccananus. 



Posterior ridge with strong devaricate ridges, 



F. maftiroli. 

 Posterior ridge widely rounded, V. nrisooJensis. 



Group of Vir^^us heccarianns. 



Shell having the posterior ridge high and rounded, out- 

 lined on each side by a sulcus, the radiations from this ridge 

 rather fine : surface concentrically sculptured. 



ViRGiJS BECCARTANUS (Tappcrone-Canefri) . 



Shell elongated, subinflated, inequilateral, the base line near- 

 ly straight ; dorsal line almost parallel with the base line as 

 far back as the hinder end of the ligament, behind which point 



