134 



Subfamily HYRIN^E. 



Male and female shells alike, with beak sculpture radial or 

 zigzag-radial ; marsupium occupying the inner gills only. 



Distribution. Southern arid Eastern Asia ; Malay Archipelago ; 

 Solomon Islands ; Australia ; New Zealand ; Tasmania ; South 

 America ; and Africa. Several of the genera are found in the 

 Indian Region. 



Genus UNIO. 



Unio, Retzius, Diss. Hist. Test. Gen. 1788, p. 16 ; Bruguiere, Choix 



de Memoires, i, 1792, p. 106. 

 Limneea, Poli (pars), Test. utr. Sic. i, 1791, p. 31. 

 Lymnium, Oken, Lehrbuch, 1815, p. 237. 

 Elliptic, Rafinesque, J. de Phys. t Hist. Nat. 1819, p. 426. 

 Mysca, Turton, Conch. Ins. Brit. 1822, p. 243. 

 Canthyria, Swainson, Tr. on Mai. 1840, p. 278. 

 Uniomerus. Conrad, Proc. Acad. Nat. Sci. Philadelphia, vi, 1853 y 



p. 268. 



TYPE, Unio tumidus, Retzius, from Northern and Central 

 Europe, Siberia. 



Range. Europe, Siberia, Asia Minor, Assyria, N. Africa, and a 

 single species recorded from Kashmir. 



Shell inequilateral, ovate or elongate, generally cuneate, ridged 

 vith concentric growth-lines ; umbones moderately large, generally 

 corrugately sculptured ; hinge possessing one pseudocardinal and 

 one lateral tooth in the right valve and two pseudocardinals and 

 two laterals in the left valve ; umbonal cavity shallow. 



The following description of the animal is taken from Simpson's 

 work on the Unionidse.* " Animal having the inner branchiae 

 free from the abdominal sac for from one-half to their entire 

 length ; marsupium occupying the whole length of the outer 

 gills only, forming a thick, smooth pad when filled with young ; 

 gills united to the mantle behind to their extreme points, or very 

 nearly so ; papilla? on branchial and anal openings unbranched ; 

 superanal opening always closed below." 



< Section LYMNIUM. 

 Lymnium, Oken, Lehrbuch, 1815, p. 237. 



TYPE, Unio pictorum, Retzius ; Europe. 



Range. Europe ; N". and C. Asia. 



Oken's description being totally inadequate, it has been ampli- 

 fied by Simpson as follows : " Shell generally smooth ; beak 

 sculpture broken, often somewhat corrugated or pustulcms; 



* Washington, D.O., Smithsonian Inst. Nat. Mus. Proc. xxii, 1900, p. 680. 



