CHEUDONOPSIS 1369 



shaped gape ; surface delicately, concentrically striate, with 

 faint traces of radial sculpture; epidermis yellowish-green, 

 brilliant and having a nietallic luster, sometimes feebly rayed ; 

 muscle scars shallow, three in front (two of which are united), 

 and two behind ; hinge edentulous ; nacre brilliant, violet-tinted. 



Length TOO, height 24, diam. at beaks 14, at posterior ex- 

 tremity 20 mm. 



Length TOO, height 28.5, diam. at beaks 13. 5, at posterior 

 end 26 mm. 



Kongo region. 

 S hatha hirundo von Martens, S. B. Nat. Fr., 1881, p. 122; 



Conch. Mitth., II, 1883, p. 139, pi. xxvii. 

 Chelidonura hirundo Rochebrune, Bull. Soc. Mai. Fr., Til, 



1886, p. 2, pi. I, figs 5, 6. — VON Martens, S. B. Nat. Fr., 



1886, p. 161, pi. I, figs. 5. 6. 

 Chelidonopsis hirundo Simpson, Syn., 1900, p. 906. ' ; 



A remarkable form, apparently related to some of the Mu- 

 telas. A specimen before me has each posterior ridge devel- 

 oped into a tube after the manner of the young spines of 

 Unio spinosus. Both tubes are more or less open behind ; one 

 is filled in part with nacreous matter, the other is open through- 

 out its length. Behind these tubes in each valve is a secondary 

 somewhat aborted tube. The anterior rostrum on each valve 

 is slightly spreading. 



Chelidonopsis roubaudi Germain. 



■'The general form of the shell is elongated ellipsoidal, re- 

 calling that of Psammohia vespertina, much compressed, gap- 

 ing at both ends ; anterior region regularly rounded, decidedly 

 cut away below ; posterior region twice as long, having on 

 each valve a projecting carina, which extends from the beak 

 to a point a little above the posterior extremity ; dorsal margin 

 subconcave, slightly ascending; ventral margin convex, al- 

 most parallel to the dorsal margin ; antero-dorsal angle acute, 

 postero-dorsal angle rather blunt ; beaks compressed, not prom- 

 inent, somewhat eroded, situated almost exactly at the anterior 

 third of the shell ; posterior ligament strong, very long, 36 

 mm. ; anterior ligament thin and delicate ; anterior impressions 



