664 PROCEEDINGS OF THE ACADEMY OF [DeC, 



About twenty specimens of this species were taken from the roots 



of the water hyacinth on the left bank of the main affluent of Lake 



Papar5% In view of the difficulty of the group, several closely 



similar forms being described, some of them imperfectly, it has been 



thought best to leave this species nameless. The description and 



figure should enable some future reviser to determine the Lake 



Papary form. 



UNIONID^. 



Genus CASTALIA Lamarck. 

 Castalia ambigua Lamarck. 



An. sans Vert., VI, 1819, p. 67. 



Tetraplodon ambiguus Lam., Simpson, Proc. Nat. Mus., Vol. XXII, p. 863. 



One perfect, dead specimen and with several valves, were taken just 

 below the Guajara-Assii Falls, and about twenty dead specimens 

 were taken on a sand bank below Camp 43, M. & M. R. R.; three 

 valves taken on the Ilha de Goyana, in the Rio Tapajoz, and one 

 from the Ilha Itaiuna, near Cameta, Rio Tocantins, were sent from 

 the Goeldi ]\Iuseum. 

 Castalia quadrilatera Orbigny. 



Guerin, Mag. de ZooL, No. 62, 1835, p. 42. 



Tetra'plodon quadr Hater um (Orbigny), Simpson, I.e., p. 864. 



A single mature specimen taken in the Rio Jamauchim was sent 

 from the Goeldi Museum. 



Genus HYRIA Lamarck. 

 Hyria corrugata Lamarck, var. exasperata (Sowerby). 



Hyria exasperata Sowerby, Conch, Icon., XVII, 1869, pi. 2, fig. 3. 



Simpson {I.e., p. 869) unites the variety with the type. About a 

 dozen specimens were taken at Camp 43, M. & M. R. R., all of which 

 were almost exactly alike, and all of which correspond so exactly 

 with Sowerby's figure that it seems to the writer that the variety 

 must be valid. 

 Hyria jamauchimensis n. sp. PL XXVII, figs. 8, 9. 



Shell rather light, compressed, subrhomboidal, inequipartite; 

 beaks low, eroded, but still showing signs of strong radial sculpture 

 which extends over the disk about half way to the margin, the central 

 bars anastomosing and dividing irregularly, a few of them extending 

 brokenly nearly to the edge of the shell; anterior and posterior bars 

 nearly horizontal and more defined; growth lines close, but fairly 

 distinct, decussating the radial sculpture throughout; epidermis 

 rather delicate, light yellow-olive; a small anterior wing with a 

 slightly upturned angle and more distinctly winged posteriorly, the 



