NAUTILUS. 



Voi,. XXIV. JANUARY, 1911. No. 9 



NOTES ON OEIENTAL UNIONIDJE. 



BY L. S. FUIEUSON. 



PSEUDODON. 



This genus of shell verges on one hand into Nodularia and on an- 

 other is close to Virgus. A couple of specimens of Pseudodon restispi- 

 natus Martens show an outline and sculpturing very much like Virgus, 

 while specimens of Nodularia (probably) brandtii from Japan show 

 a very close kinship to Pseudodon in its teeth and general facies. 

 Several specimens of Pseudodon having beak sculpturing show that 

 the genus has essentially concentric and not radial sculpture. 

 Hence the genus must be removed from the Hyriance and placed in 

 the Unionince (page 515). One specimen has perfect beaks, and in 

 this species, P. resuspinatus Martens, the sculpture consists of a 

 double row of Vs, one with the angle pointing down the posterior 

 umbonai slope, the other down the anterior slope, and the arms 

 coalescing in the middle of the shell thus, W. As the shell grows 

 the angles become greater, so that on the body of the shell a roughly 

 concentric sculpture finally results. 



NODULARIA. 



Considerable changes will have to be made in this genus. Nodu- 

 laria grayana Lea, N. japanensis Lea, N. invoJnta Benson, N. pazii 

 Lea, N. crispata Gould form a heterogeneous assemblage truly. 

 The situation is but little relieved by the several sections into which 

 the genus is cut. 



Mr. Simpson himself, in letters, states that because the N. coffer 

 baa been found to carry eggs in the inner gill, the section l 'Cafferia" 



