ortmann: south American naiades. 561 



Anal opening closed above; closed part three to four times as long as the oj^en 

 part, the latter slit-like, shorter than the branchial, and separated from the latter 

 by a solid mantle-connection. Branchial opening with jiapilke, closed in front 

 by a firm union of the inner mantle-edges, or, more rarely, open and without this 

 connection. Palpi rather large and slightly produced ])osteriorly, with stronglj- 

 curved lower margins. Their posterior margins are connected for about one- 

 third of their length. 



Gills of the usual shape, the inner much wider in front than the outer, its 

 anterior end close to the pali)i. Inner lamina of inner gill entirely connected 

 with abdominal sac. Non-marsupial gills with scattered interlaminar connec- 

 tions. Marsupium of the female located in the inner gill, but it does not occupy 

 aU of this gill, but only a portion in the middle, leaving free a larger part anteriorly, 

 and a smaller posteriorly, so that the marsupium appears shifted slightly backwards. 

 Interlaminar connections of marsupium arranged in interrupted septa. 



Genus Hyria Lamarck (1819). 

 Hyria Lamarck, 1819, p. 81; Simpson, 1900, p. 868; 1914, p. 1211. 



This genus is characterized by the alate shape of the shell, possessing wings 

 both at the anterior and posterior end of the upper margin. In addition the 

 radial beak-sculpture is well developed, covering a considerable part of the shell, 

 the posterior ridge is rounded and broad, and the pseudocardinals are much com- 

 pressed. The hinge-teeth may be somewhat corrugated, but they do not possess 

 distinct vertical ridges. 



The distribution of this genus is restricted to the basin of the Amazon and the 

 rivers of Guyana. A key to the species has been furnished by Simpson (19t4, p. 

 1212), but some of the species may be only forms of others. 



38. Hyria corrugata Lamarck (1819). 

 Hyria corrugata Lamarck and H. transversa Hupe, Simpson, 1900, pp. 868, 869; 



1914, p. 1212, 1215. 



Type-locality. — Unknown. 



Other Localities. — Rio Solimoes (= middle Amazon) {Triplodon rugosum Spix, 

 Wagner, 1827, p. 35); Rio Yavari, Brazil (southern tributary of Amazon, forming a 

 boundary between Brazil and Peru) (Haas, 1916, p. 9, 47). 



New Locality. — Sand-bar of Rio Tapajos, Santarem, Para, Brazil (J. D. Hase- 

 man coll., December 6-12, 1909). About fifty specimens, among them two fe- 

 males with soft parts. 



