92 NOTICES OF BOOKS. 
Cork, though less searce in Connemara, andis identical with S. elongatum, 
Barker. See Quarterly Journal of Mier. Science, vol. ix. n.s., p. 424]; 
} form v i 
[rather small, about one-third broader than long ; constriction deep, 
expanding; segments elliptic, divergent (obversely lunate), angles 
furnished with short geminate divergent spines, on f 
at each side a pair of intermediate, short, bifid spines ; surface granu- 
ate, granules in transverse lines; end-view triradiate, sides concave. 
10-12 minute papille occupying a similar osition ]; Pentium mimi- 
tissimum, 0.s. fs minute subelliptic unconstricted form, about a half 
longer than broad, a smooth yellowish-coloured membrane, a thick- 
cire in end-view and showing a minute papilla on each side, the 
latter circulari-triangular in end-view and showing three equidistant 
blunt papille. These forms seem to point, asit were, toa transition to 
the genus Didymoprium. Judging, too, from specimens in spirit, the 
s 
been unable to obtain quite phyll g Pp ; 
form shows the lateral, tooth-like projections considerably more proml- 
nent and divergent than that of N ordstedt. ] 
mong the more noteworthy forms not new occurring to the 
author in Norway are Micrasterias denticulata, Bréb., with basal and 
middle lobes thrice divided ; 1. Lhomasiana, Arch. ; M. conferta, Lun- 
dell [not found in Britain] ; M. mucronata, Dixon. The large Luastra 
in Britain. “ Forma genuina ” of Nordstedt might possibly be better 
denominated Cosmarium reniforme (Ag.)—segments reniform, in end- 
