I2o8 CASTA!,] ELLA 



which causes a sinuosity in the outHne ; epidermis brownish- 

 yellow ; hinge crenate ; one pseuclocardinal in the left valve and 

 two in the right, which are jagged or somewhat broken up; 

 laterals elongate and striate. 



Castalina orbignvi (Hupe and Deville). 



Shell subrhomboid, almost or quite equilateral, ponderous, 

 but little inflated; beaks high and rounded, apparently without 

 sculpture; posterior ridge well developed, narrowly rounded, 

 terminating in a blunt point at the base of the shell ; above it 

 there is a wide, radial furrow that ends in a slight sinus below ; 

 hinge line arched, straight and sloping in front of and behind 

 the beaks; posterior end obliquely truncate; base almost 

 straight; anterior end cut away below, narrowly rounded 

 above; pseudocardinals ragged, laterals short; nacre whitish, 

 thickened in front. 



Length 97, height jy, diam. 50 mm. 



Upper Amazon. 

 JJnio orbigiiyi Hupe and Dkville, Rev. et Mag^., 1850, p. 645, 



pi. XVI, fig. I. 

 Margaron (Unio) orbignyi Lea, Syn., 1852, p. 24; 1870, p. 37. 

 Castalina orbignyi Simpson, Syn., 1900, p. 866. 

 Unio orbignyana Hupe, Moll. Nouv., IH, 1857, p. 83, pi. xvii, 



fig. I. 

 Unio d'orhignyanns Sowerp.y, Conch. Icon., XVL 1868, pi. 



xcvi, fig. 523. 

 Unio orbignyamis P^tel, Conch. Sam., HL 1890, p. 162. 



A large species, which is more nearly rhomboid in outline 

 than any of the others. The surface appears to be strongly 

 and irregularly, concentrically striate ; the beaks are, according 

 to the authors, without sculpture, but the specimen figured is 

 slightly eroded in this region. The epidermis is light brown. 



Genus CASTALIELLA Simpson, 1900. 



Castaliella Simps'on, Syn., 1900, p. 866. 



Shell subtriangular, greatly inflated, subsolid, and strongly 

 sulcate ; beaks high, the sculpture regularly radiate ; posterior 

 ridge well defined and sharp; liinge line narrow, arched; there 



