160 MOLLUSCA OF THE 



38. Paludina Hamiltoni Metcalfe. 



Metcalfe, Proc. Zool. Soc. London, 1851, p. 73. — 

 Reeve, Conch. Icon. fig. 37. 



Localities: Mouth of the Mandai River, May 1894(Bütti- 

 kofer). — Sai River, a branch of the Ketoengau (Moret). — 

 Sintang (Büttikofer). 



39. Clea nigricans Adams. 



Adams, Proc. Zool. Soc. London, 1855, p. 119. 

 Locality : Sibau River (Büttikofer). 

 One young specimen. 



40. Unio Velthuizenij n. sp. 

 (Plate 4, fig. 1). 



Shell winged, nearly triangular, moderately inflated, 

 very inaequilatera] , concentrically striated and folded; 

 umbones rather obtuse, decorticated, consequently no pecu- 

 liar sculpture visible ; epidermis dark brown , if held against 

 the light it is yellow, with numerous green rays; upper mar- 

 gin nearly straight anteriorly, ascending behind ; anterior 

 margin meeting the upper one nearly rectangularly, then 

 rounded , passing insensibly into the ventral margin which 

 is long and slightly sinuous; posterior margin passing by an 

 obtuse angle into the ventral, by a distinct angle into the 

 superior one, bent inwards above , straight in the middle , 

 rounded below. Two obtuse angles run from the beaks 

 towards the infero-posterior angle. Posterior slope with 

 concave sides, forming a triangular wing. Nacre iridescent, 

 bluish white; anterior scars irregular, rather small, posterior 

 ones rounded , pallial scar distinct. Hinge not strongly 

 developed, cardinal teeth elongated, obtuse, one in each 

 valve, in the right valve a rudimentary second one; lamel- 

 lae arcuate, elongated, one in the right, two in the left 

 valve, the uppermost of these latter very obsolete. 



Long. 94, alt, near the umbones 42, near the wing 

 61 mill.; diam. 29 mill. 



Notea from the Ley den IVluseum, "Vol. XVII. 



