I 130 PARUIvVSIA 



Unio ii^^csiaiiiis \c)n Marti- ns, Besch. Dents. Ost-Af., 1897, p. 



234, pi. VI 1, %. 7. 

 Parreysia ngcsianus Simpson, Syn., Kpo, p. 847. 



This sjoecies has two radial rows of tubercles, which some- 

 times become somewhat \-shaped, that radiate from the beaks. 

 The base is slii^htly produced in the center. 



The following untigured species are placed in this group by 

 von Martens : 

 Unio billotianns Charmes, Bull. Soc. Mai. Fr., II, J885, p. 



170, Bagamoyo, Central Africa. 

 Unio euphymus Charmes, Bull. Soc. Mai. Fr., II, 1885, p. 171, 



Bagamoyo. 

 Unio diimeslcaniis Charmes, Bull. Soc. Mai. Fr., II, 1885, p. 



168, Bagamoyo. 



Group of Parreysia fabagina. 



Shell very small and solid, inflated, compressed on the sides, 

 rhomboid, with a high, sharj) posterior ridge and high beaks, 

 having zigzag-radial sculpture sometimes extended over the 

 disk, the posterior slope furnished with upcurved plications ; 

 pseudocardinals heavy, torn, one in the right valve, two in the 

 left : muscular impressions circular, the anterior very deep. 



Parreysia ea!3.vgina (Deshayes). 



Shell very solid, small, inflated, rhomboid, inequilateral ; 

 beaks full and elevated, with irregular zigzag- radial sculpture; 

 posterior ridge high, angled, rather close to the edge of the 

 shell, curved, ending in a sharp point near the base of the 

 shell ; anterior end rounded ; base line lightly arcuate ; dorsal 

 outline arched ; dorsal slope obliquely subtruncate, there being 

 a low angle where it joins the dorsal part of the shell ; epider- 

 mis fuscous-green ; pseudocardinals thick ; laterals strong 

 greatly curved ; nuiscle scars small, the anterior ones deep, 

 the posterior ones semilunar ; nacre silvery. 



Length 17, height 12, diam. ii mm. 



Mekong River. Cambodia. 



