VIRGUS 1 153 



Unio wattiroli Tappkrone Canefri, Ann. Mus. Genov., XIX, 



1883, p. 292, pi. XI, fig-. I. 

 Virgus mattiroH Simpson, Syn., 1900, p. 852. 

 Virgiis mattirolil Haas, Con. Cab., Unio, 1910, p. 131, pi. xiii, 



fig. 2. 



Apparently more solid than U. beccarianiis. It is not so 

 greatly elongated as that species and may be at once distin- 

 guished bv the very strong, divaricate sculpture along the 

 entire length of the posterior ridge. 



Group of Virgus misoolensis. 



Posterior ridge merely rounded, with radiating folds scat- 

 tered over the shell, pseudocardinals two in the left valve and 

 one in the right. 



ViRGus MisooLKNSJS (Schepman). 



Shell elongated, rather compressed, very inequilateral, near- 

 ly smooth, with numerous, fine, concentric striae; beaks but 

 slight) v prominent, with conspicuous, radiating folds, extend- 

 ing more or less over the disk of the shell ; there are a few 

 radiating grooves on the anterior end, and microscopic, radi- 

 ating wrinkles of the epidermis on the posterior slope ; epi- 

 dermis reddish-brown in the adult, yellowish-olive-green in 

 the young state ; dorsal outline lightly arcuate from the beaks 

 to the extreme posterior end near the base ; base line almost 

 straight ; anterior end rounded ; posterior ridge full, simply, 

 widely rounded, ending near the base in a rounded point ; 

 nacre bluish-white, iridescent behind ; thicker in front ; scarce- 

 ly more than one short, thick, crenated pseudocardinal in each 

 Talve ; a small knob in the left valve may perhaps be consid- 

 ■ered a second one ; laterals club-shaped, elongated, two in the 

 left valve and one in the right ; anterior scars deep. 



Length 65, height 24, diam. 16 mm. 



Misool, Borneo. 

 Unio misoolensis Schepman. Notes from Leyd. Mus., XVIII, 



1896, p. 259, fig. 



