COSMARIUM. 215 



Cells small, a little longer than broad, deeply con- 

 stricted, sinus narrowly linear ; semicells pyramidate- 

 trapezif orm, basal angles rounded, apical angles obtuse, 

 sides convex and 5-undulate, apex truncate and 4- 

 undulate, with two series of small granules within the 



o 



margin (outer series of 13 granules, inner series inter- 

 rupted and only of 7 granules), with two prominent 

 granules (vertically disposed) in the centre of the 

 semicell just above the isthmus. Side view of semi- 

 cell elliptic-subcircular, with two almost papillate 

 granules at each side near the base. Vertical view 

 elliptic, with a prominent granule at the middle on 

 each side. 



Zygospore unknown. 



Length 34 p, ; breadth 28 ju, ; breadth of isthmus 9 JJL ; 

 thickness 17 /x. 



IRELAND.- -Creggan Lough, Gralway ! 



This little Desmid is distinguished from C. bipunctatum by 

 the form of its semicells and by the two longitudinally placed 

 granules just above the isthmus. 



192. Cosmarium distichum Nor cist. 

 (PI. LXXXVII, fig. 18.) 



Cosmarium distichum Xordst. in Botan. Notis. 1887, p. 160; Fresliw. Alg. 



K". Zeal. 1888, p. 51, t, 5, f . 16 ; De Toiii, Syll. Alg. 1889, p. 1051 ; Xordst. 



Index Desin. 1896, p. 111. 

 Ursinella disticlia Kmitze, Eevis. gen. plant. 1891, p. 924. 



Cells small, a little longer than broad, very deeply 

 constricted, sinus linear ; semicells transversely sub- 

 rectangular-elliptic, basal angles subrect angular, sides 

 convex 6-undulate-crenate, apical angles rounded, 

 apex widely truncate and smooth, with 7 granules in 

 the centre (six rather distant peripheral granules sur- 

 rounding one central granule). Side view of semicell 

 subcircular, slightly flattened at the apex, sides with 

 4 granules, and with two converging series of granules 

 (one starting from each of the upper marginal granules) 

 extending downwards to just above the isthmus. 



