﻿2i6 iiYKiorsis 



Crou]! of Ilyriof^sis 'icltliiiiccni. 



Shell somewliat inflated, rather thin, rounded behind, 

 wini^ed ; epidermis dark brown with numerous ^reen rays ; 

 nacre iridescent, lihiish-white : anterior scars irretifular, rather 

 small ; posterior scars rounded ; pseudocardinals elonc^ated. one 

 in each valve, in the rij^ht valve there beintj a secondary rudi- 

 mental one ; laterals elon<xate. arcuate, one in the rij^ht valve 

 and two in the left. 



Ihkioi'Sis VELTHi'izirNi (Schepman). 



Shell subtrianfnilar. thin, scarcely inflated, with a well-de- 

 veloj^ed, rounded jiosterior ridg'e. which is slii:j;htly double and 

 biaui^ulate. the lower rids^e the most distinct ; with a hii^h. thin, 

 posterior wing, which is rather acutely angled behind and a 

 small, obtusely angled anterior one ; base line nearly straight, 

 sometimes feebly incurved in the middle; surface finely, irreg- 

 ularly, concentrically striate, shining, yellowish-olive, faintly 

 rayed ; l>eaks low. sculpture not seen ; left valve with one pseu- 

 docardinal and two nearly straight laterals ; right valve with 

 one pseudocardinal, a small one above it, and one lateral ; 

 teeth all lamellar: muscle scars feeble; nacre bluish, tinted 

 purple, iridescent, especially on the wings. 



Length 65. height 30. to summit of wing 53. diam. 20 mm. 

 The above measurements are from what is probably a young 

 shell. 



Mandai River. T.orneo. 

 Unio velthuizcm Schkpman, Notes Leyden Mus., XA^TT, 1895, 



p. t60. pi. IV. figs. T. TO. 



Hyriopsis velthnzem Simi'.son. Syn.. 1900. p. 581. 



This shell suggests an extremely close relationship to such 

 species as Lawpsilis data and its variety poulsoni or the L. 

 in flat a. 



Group of Hyriopsis schlei:rli. 



Shell rather thin, slightly winged behind, narrowly rounded 

 before and angled at umbonal slope ; posterior ridge high and 

 rounded; beaks rather low; epidermis rough, blackish; hinge 



