1912.] H. B. Preston: The Asiatic Natades. 287 
side produced, rounded; cardinal teeth rather anteriorly situate, 
triangular, erect ; lateral teeth anteriorly very short, posteriorly 
elongate and abruptly terminating ; anterior adductor scars deeply 
impressed ; posterior scars slight ; interior of shell very slightly 
iridescent, sculptured with fine irregular ridges somewhat resem- 
bling the marks of coarse finger prints. 
Long. 45, lat. 86 mm. 
Hab.—River Tigris, Reg. No. 243+ [Type]. 
20. Unio mongolicus, Middendorff, Sib. Reise, II, 185: 
p. 277, pl: Xxvil, figs. 7, 8. 
Upper Indus, Reg. No, 595+. 
21. Unio tigridis, Bourguignat, Test. Nov. Saul. , 1852, p. 30° 
Cat. Rais. Moll., 1853, p. 77, pl. iv, figs. 7, 9,—=Umio truncatus, 
Swainson, Zool. Ill., 2nd Ser., I, 1829, pl. x,—Margarita (Umo) 
truncatus, Lea, Syn., 1836, p. 21; 1838, p. 18,—Margaron (Umio) 
truncatus, Lea, Syn., 1852, p. 26; 1870, p. 39,—Unto dignatus, 
ea seroceAc, Nat. oct. Philad.} Vil, 1863, p. 189::. Jl, Ac. Nat. 
Sci. Philad., VI, 1866, p. 51, pl. xvii, fig. 48,—Margaron (Unio) 
dignatus, Lea, Syn., 1870, p. 39,—=Margaron (Unio) tigris, Lea, 
Syn., 1870, p. 39,—=? Unio ktsonis, Kobelt, Icon., Ist sup., 1895, 
eek. pl. vily teen 2 73: 
River Tigris, Asiatic Turkey, Reg. No. 425. 
22. Unio terminalis, Bourguignat, Test. Noviss., 1852, 
feast wear. Rais. Molly) 1853, p.1 70, pl! ii, figs. 4—-6.-etc. == 
Margaron (Unto) terminalis, Lea, Syn., 1870, p. 39. 
Jordan Valley, Reg. No. +724. 
23. Unio ascia, Hanley, Rec. Biv. Shells, 1856, p. 385, pl. 
Exit, fig. 20: 
Penang, Reg. No. #235, 
24. Unio perakensis,sp.n. (PI. viii, figs. 5, 6.) 
Shell closely allied to Unio pressirostris ,' Von Martens, of which 
it may ultimately prove to be a variety, but differing from that 
species in its less cuneate form and larger size, in its less contracted 
anterior side and more obtuse and sloping posterior side. 
Long. 31, lat. 85°5, diam. 21 mm. 
Hab.—Perak, Reg. No, +156 [Type]. 
Gen. Shistodesmus, Simpson, 1900. 
25. Shistodesmus lampreyanus (Baird and Adams), 
Simpson, Syn. Naides, Proc. U.S. Nat. Mus., XXII, p. 804,—= 
Unio (Dysnomia) lampreyanus, Baird and Adams, Proc. Zool. Soc. 
London, 1867, p. 4o1, pl. xxvi, figs. 2, 2a,—Margaron (Unio) 
lampreyanus Lea, Syn., 1870, p. 30. 
Shanghai, Reg. No. 695. 
1 Nachrichtsbl. d. D. Malak. Ges., 1900, p. 14. 
