I 134 PAKKKYSIA 



Unio nyaSs<:acnsis var. Smith, Pr. Zool. Soc. Lond., 1881, p. 



298, pi. XXX i\', fig. 34. 

 Grandidieria njijiensis Bourgitignat. Bull. Soc. Mai. Fr., II, 



1885, p. 7. 

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



Mr. Smith does not give a description of this form, which 

 he figured in the Proceeding of the Zoological Society and 

 referred to Unio nyassacnsis Lea, as a variety. There is some 

 little confusion about it, as he refers to fig. 34/7 on pi. xxxiv, 

 and there is no such number. His 340 seems to be 

 typical nyassacnsis and the 34 a different species, being tri- 

 angular ovate and smoother than nyassacnsis. Bourguignat 

 suggested the name njijiensis for this species, but his account 

 of the shell is not accessible as I write. I can not therefore 

 give any account of the beak sculpture, nacre, solidity or diam- 

 eter of this form. 



Parreysia aferui.a (Lea). 



Shell rhomboid, solid, convex, inequilateral ; beaks neither 

 very full nor high, with strong, zigzag sculpture and corru- 

 gations, which extend over the entire surface of the disks ; 

 posterior ridge full, feebly double, ending in a faint biangula- 

 tion at the base of the shell ; anterior end rounded ; base line 

 almost straight ; hinge line lightly arched, ending in an angle 

 where it joins the obliquely truncate dorsal slope; epidermis 

 dirty ash colored, not shining ; hinge solid ; pseudocardinals 

 much split ; laterals double in each valve ; muscle scars impress- 

 ed : nacre bluish-white. 



Length 29, height 20, diam. 12.5 mm. 



Lake Nyassa.- 

 Unio afenda Lea, Pr. Ac. N. Sci. Phila., YIII, 1864, P- io9- 

 Unio afernlns Lea, Jl. Ac. N. Sci. Phila., VT, 1886, p. 34, pi. 



xin, fig. 34; Obs., XL 1867, p. 38, pi. XIII, fig. 34. 

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

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



It is quite likely that this is the same as Lea's Unio nyassacn- 

 sis, but I have only seen a single shell, the type, and do not feel 



