﻿508 IIYUKU'SIS 



oiulary ridge at some distance above it, the main ridge ends 

 in a sharp point at the extreme post-basal part of the shell, 

 the secondary ridge emls in an obtuse angle above it ; liga- 

 ment concealed in young shells, long and exposed in old ones ; 

 beaks low, their sculpture not known ; epidermis black and 

 somewhat shining, covered with scattered, low, pustule-like 

 blisters, which are often arranged in concentric rows ; left 

 valve with a long, low, pinched up anterior pseudocardinal and 

 a feeble posterior one, with two long, curved laterals ; right 

 valve with a long, irregular pseudocardinal, a small one above 

 it and one lateral, all the pseudocardinals showing a tendency 

 to break into denticles ; beak cavities shallow, with an irreg- 

 ular row of pits ; anterior muscle scars distinct, well impressed, 

 small ; nacre bluish-white with a slight pallial sinus. 



Length 135, height, without the wing, 56, height with the 

 wing 80, diam. 25 mm. 



Southeastern Asia, including Cambodia, Siam, and the Ma- 

 lay Peninsula. 

 Unio delphinus Gruner, Arch, fiir Naturg., I, 1841, p. 276, 



pi. IX, figs. I, la-c. — Dei.esskrt, Rec. Coq. Lam., 1841, pi. 



XIX, ligs. 3, 3a, 3&. — Lea, Tr. Am. Phil. Soc, VIII, 1843, p. 



218, pi. XVII, fig. 35; Obs., Ill, 1842, p. 56, pi. XVII, fig. 35. 



— Kuster, Conch. Cab. Unio, 1852, p. 18, pi. 11, figs. 2-4. — 



Haneey, Biv. Shells, 1856, p. 381, pi. xx, fig. 44. — Chenu, 



Man., 1859, II, p. 143, fig. 707. — Sowerby, Conch. Icon., 



XVI, 1866, pi. xi.ii], fig. 238. 

 Margaron (Unio) delphiniis Lea, Syn. 1852, p. 19; 1870, p. 28. 

 Metaptera delphinus Morlet, J. de Conch., XXXVII, 1889, 



p. 165. 

 Unio megaptcnis Morelet, J. de Conch., XII. 1863. p. 159. 

 Hyriopsis bialatiis Simpson, Syn., 1900, p. 579. 

 Unio delphinGpterus Datttzenrerc. and Fischer, J. de Conch., 



LIII, 1905. p- 456. 



A most striking species, having when young and perfect a 

 very high wing. Gruner's name was used previously by 

 Spengler for a Unio and the term megapterus of Morelet was 

 applied by Rafinesque to a Metaptera (Unio) and used by 

 Chenu under the generic name Unio before 1863. 



The scattered pustules, like blisters, is a peculiar feature. 



