IQI2. | H. B. Preston: The Astatic Navades. 307 
Genus Trapezoideus, Simpson, 1900. 
81. Trapezoideus foliaceus (Gould), Simpson, Syn. Naiades, 
Proc. U. S. Nat. Mus., XXII, p. 858,—Unio foliacea, Gould, Proc. 
Bost. Nat, Hist. Soc., I, 1843, p. 141,=Uvnio foliaceus, Catlow and 
Reeve, Conch. Nom., 1845, p. 59; Hanley and Theobald, Conch. 
Ind., p. 19, pl. xlii, fig. 3,=Margaron (Unio) foliaceus, Lea, 
Syn., 1852, p. 39; 1870, p. 62,—Unto peguensis, Anthony, Am. 
ple Conch, 1665, p: 351, plo xxv, fig. 2; Sowerby, Conch. 
Icon., XVI, 1868, pl. xcv, fig. 519,—=Margaron (Unio) peguensis, 
Leay Syl. =670, p= 51. 
Bhamo (J. Anderson), Reg. No. 4797; Pegu (W. T. Blanford), 
Rees No —a-., Pest, Regu Nos 2035) 
81a. Var. zayleymanensis (Nevill, MS.), var. n. 
Shell thinner and smaller than the typical form, more pro- 
duced anteriorly and much more obtuse posteriorly, the slight 
curve in the ventral margin is also absent. 
Hab.—Bhamo (J. Anderson), Reg. No. 2575 [Type]; also from 
Bhamo, Reg. No. 2572; Zayleyman (J. Anderson), Reg. No. 2374. 
82. Trapezoideus misellus (Morelet), Simpson, Syn. Nai- 
ades, Proc. U.S. Nat. Mus., XXII, p. 859,—=Unio misellus, Morelet, 
ide, Conchy iil 1865. p.2u; ser Concl., IV; 1875, p. 341, pl: 
Mivwlie. 2. ——-U 070 stamensts,. Vea, Proc. Ac. Nat. Sci., Philad., 
ReetSOo ep ks3. Il Ne Nat oci.. Philad:) VI,1868, p. 279, pl. 
RVI een nos Obs. . Sil er6g,. p. 30, ply xxxvili, fig. 93, 
=Margaron (Unio) stamensis, Lea, Syn., 1870, p. 57. 
Tenasserim, Lower Burma, Reg. No. 597+; Irrawaddy River 
at Sagaing (J. Coggin Brown), Reg. Nos. +789=+_, 
82a. Var. subclathratus, von Martens, Arch. fiir Naturg., 
p. 44, pl. vi, fig. 3. 
Sheinmagah, Shwebo Dist., Burma, Reg. No. 356s, 
83. Trapezoideus pallegoixi (Sowerby), Simpson, Syn. Nai- 
ades, Proc. U.S. Nat Mus., XXII, p. 859,=Anodon pallegotxt, 
Sowerby, Conch. Icon., XVII, 1867, pl. xvii, fig. 17,—Anodonia 
pallegotxt, Clessin, Conch. Cab. Ano., 1876, p. 210, pl. Ixiv, 
fig. 6. 
84. Trapezoideus exolescens (Gould), Simpson, Syn. Nai- 
ades, Proc. U.S. Nat. Mus., XXII, p. 859,=Unio exolescens, Gould, 
Proc. Bost. Soc. Nat. Hist., 1843, p. 141; Hanley and Theobald, 
Conch. Ind., p. 43, pl. evii, fig. 5,—Margaron (Unio) exolescens, 
Lede Wyte, 185 27,p1032 22 £870, pi 51; 
Bhamo, Reg. No. 222%, 
Genus Arconaia, Conrad, 1865. 
85. Arconaia lanceolata (Lea), Simpson, Syn. Naiades, Proc. 
U.S. Nat. Mus., XXII, p. 860,—Triquetra lanceolata, Lea, Proc. 
Ac. Nat. Sci., Philad., VIII,-1856, p. 79,—Hyria lanceolata, Tea, 
