PARRlvYSIA I I 15 



posterior ridge well developed, narrowly rounded or suban- 

 gular ; dorsal slope often obliquely truncate, usually covered 

 with strong, subradial folds; epidermis usually dirty bottle- 

 green, sometimes slightly variegated and faintly rayed, at other 

 times it is a lurid, greenish-brown, scarcely shining ; hinge line 

 arched ; teeth only moderately strong ; pseudocardinals some- 

 what divided, but much less so than in most related species ; 

 beak cavities only moderately deep; nacre dull, bluish to ilesh- 

 colored, often lurid in the cavities. 



Length 52, height 39, diam. 24 mm. 



Length _|4. height 35, diam. 21 mm. 



Burma, India. 

 Unio taz'oyensis Gould, Pr. Bost. Soc. N. Hist., 1, 1843, p. 140. 



— KusTKR, Conch. Cab. Unio, 1856, p. 166, pi. XLvm, fig. 2. 



— Retjvk, Conch. Icon., XVI, 1864, pi. xiii, fig. 49. — Han- 



i.EY and Theobald, Conch. Ind., 1876, p. 62, pi. cliv, figs. 



6, 7- 

 Margaron (Unio) tai'oyensis Lea, Syn., 1870, p. 31. 

 Parreysia tavoycnsis Simpson, Syn... 1900, p. 843. 

 Unio sai'oycnsis P.-ETEL, Conch. Sam., III. 1890, p. 166. 

 Unio parnia Ben.son. Sowerby, Conch. Icon., XVI, 1868, pi. 



xcv, fig. 514. — Hanley and Theobald. Conch. Ind., 1876, 



p. 61, pi. CLIV, fig. I. 



Close to corrugata, but usually more covered with sculpture 

 and having a dirty greenish or brownish epidermis. The 

 specimen represented by figure 7 on plate cliv in the Conch- 

 ologia Indica is brighter colored than any I have seen. The 

 pseudocardinals are less ragged than in cornigata and allied 

 forms. 



I am inclined to believe that Unio parma Benson is a some- 

 what elongated form of this, as there is a specimen of taz'oy- 

 ensis from Gould in the Lea collection that is much like the 

 figure in the Conchologia Indica. 



Y^r. tricuiboJtis (Benson). 



This seems to me to be a short, pale colored variety of 

 tavoyensis, in which the disk is almost free of sculpture. Unio 

 houngdaranicns Tapperone-Canefri, of which specimens from 



