PARREYSIA I 133 



Parrkysia kirkii (Lea). 



Shell short, snbtriangular, subintiated, solid ; beaks very 

 high, full, their sculpture consisting of zigzag, su'bnodulous 

 ridges ; this sculpture reappears feebly in various parts of the 

 disk, the posterior slope and upper anterior end being plicate ; 

 beside this there are irregular, concentric ridges and feeble 

 radial grooves on the anterior end ; posterior ridge high, sub- 

 angular, with one or two faint ridges above it ; lunule distinct, 

 narrow ; anterior end narrowly rounded below, obliquely trun- 

 cate above ; base line nearly straight ; outline of dorsal slope 

 obliquely rounded from the beaks to the rather sharp basal 

 point ; epidermis greenish, feebly rayed, with two or more 

 dark rays on the dorsal slope; hinge strong, arched; pseudo- 

 cardinals very ragged ; laterals heavy, short, treble in the left 

 valve, double in the right ; muscle scars impressed ; nacre 

 bluish-white, thicker in front. 



Length 32.5, height 28, diam. 16 mm. 



Lake Nvassa. 

 Unio kirkii Lka, Pr. Ac. N. Sci. Phila., 1864, p. 108 ; Jl. Ac. N. 



Sci. Phila., VL t866, p. 32, pi. xii, fig. 30; Obs., XI, 1867, 



1). 36, pi. xir, fig. 30. 

 Margaron (Unio) kirkii Lea, Syn.. 1870, p. 30. 

 Parreysia kirkii Simpson, Syn., 1900, p. 848. 



Close to nyassaensis but higher in proportion to length, 

 more triangular, smoother and having a greener epidermis. 

 I have only seen the type. 



Parreysia ujijiensis (Bourguignat). 



Shell ovate rhomboid or ovate triangular, subinflated, in- 

 equilateral ; beaks high and full, rather sharp ; anterior end 

 rounded and very slightly truncated in the middle ; base line 

 evenly curved ; dorsal outline high at the beaks, arched ; pos- 

 terior end slopingly truncate, subangulate where it joins the 

 dorsal part ; posterior ridge full, subangulate, ending in a point 

 a little above the basal line ; surface with slight, concentric 

 sculpture with zigzag or wrinkled sculpture above on the 

 anterior end and on the dorsal slope. 



Length 29, height 20 mm. 



Lal<e Tanganyika. 



