150 UNioNiD.i:. 



285. Pseudodon (Trigonodon) peguensis (Anthony). 



Monocondylaa pequensis, Anthoiiv, Am. Journ. Conch, i, 1865, 



p. 20o, isl. ] 7, fig. 2. 

 Margaron (Monocondi/lcea) iieyuensis, Lea, Syn. 1870, p. 73. 

 Psetidodon crcbristriatum Tar. j;e/7«e??s/s, H. & T.. C. I. 1876, p. 5, 



pi. 9, fig. 5. 

 Psendodo7i (Trigonodon) crehristriatus var. peguensis, Simpson, 



WashiDgton, D.C., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, 



p. 835. 



Original description: — Shell smooth, rhombic-ovate, inequilateral, 

 somewhat iuflated, sub-biangular behind ; substance of the shell 

 thick; beaks rather prominent, eroded, but apparently not undu- 

 lated ; ligament short, thin ; epidermis dark brown or nearly 

 black, smooth over the umbones and on the anterior portion o£ 

 the shell, but having the sub-truncate posterior portion nearly 

 covered with distinct corrugated folds, more prominent near the 

 hinge margin ; cardinal teeth prominent, curved and slightly 

 bilobed, particularly in the right valve; anterior cicatrices con- 

 fluent ; dorsal cicatrices deeply impressed, placed in a curved line 

 under the beaks ; nacre light salmon-colour and very iridescent. 



Long. 57, lat. 81, diam. 33 mm. 



ffab. Peeru. 



Yar. crebristriatiis (Anthony). 



Monocondyl<ea crehristriata. Anthonv, Am. Journ. Couch, i, 1865, 



p. 205, pi. 18, fig. 1. 

 Trigonodon crebri striata, Conrad. Am. Journ. Couch, i, 186-5, 



p. 233. 

 IJnio crehristriatus, Sowerby. Conch. Icon, xvi, 1868, pi. 95, 



Margaron {Monocoyidylcva) crcbristriata. Lea. Syn. 1870, p. 72. 

 Pseudodon crehristriatus, H. & T., C. I. p. 5, pi. 9, fig. 3. 

 Unio vondembuxchi, Sowerby, Conch. Icon, xvi, pi. 95, fig. 518. 

 Pseudodon {Trigonodon) crehristriatus, Simpson, Washington, IJ.C, 

 Smiths. Inst., Nat. Mus. Proc. xxii. 1000, p. 835. 



Original description. — Shell rhombic, strongly striate, very 

 inequilateral, depressed, bi-angular behind; substance of the shell 

 rather thick ; beaks not pi-omment, eroded, having no indication 

 of any undulations at the tip; epidermis light brown, with occa- 

 sionally broad green rays on the posterior slope ; the umbones 

 and, indeed, llie surface is covered with crowded, fine, crenulose 

 striie, which, on the posterior slope, are crossed at right angles 

 with prominent, regular folds ; cardinal teeth prominent, erect, 

 bilobed in the left valve ; anterior cicatrices deeply impressed, 

 distinct ; postei'ior cicatrices confluent and indistinct ; dorsal 

 cicatrices small, but distinct, and placed at the base of the pro- 

 minent tooth in the left valve, while in the right valve they are 



