C08MAEIUJJ. 



Sweden. Denmark. Bornholm. X. Russia. Xova 

 Zembla. Spitzbergen. United States. Brazil. 



C. Debaryi is an uncommon species which should be care- 

 fully compared with C. quct'lrntum and C. pli<'t.nm. Apart 

 from differences of external form and proportions, it is some- 

 what larger than either of these species and differs signally 

 in the nature of its chloroplasts. There are about five 

 parietal chloroplasts in each semicell, often more or less 

 united towards the apex, and somewhat peculiar in the 

 possession of numerous, small, peripheral lobes. These 

 chloroplasts are similar in general features to those of C. 

 tessfilatum (Delp.) Xordst., but are more irregular (vide 

 LutkemiUler, ' Chlorophyllkorper Desm./ 1893, t. 3, f . 22-25). 

 In the centre of each semicell is a vacuole, which often stands 

 nut so conspicuously as to give the appearance of a large 

 central pyrenoid. 



84. Cosmarium exiguum Arcb. 

 (PI. LXX, fig. 17-19.) 



Cosmarium cxijuum Arch, in Proc. Dubl. Xat. Hist. Soc. 186i, p. 49, t. 1, 

 f. 32, 33 ; Eabeiih. Flor. Europ. Alg. Ill, 1868, p. 164 ; Lund. Desm. 

 Suec. 1871. p. 43; Cooke, Brit. Desm. 1886, p. 92, t. 43, f. 4: Xordst, 

 Freskw. Alg. X. Zeal. LSSS, p. 58, t. 6, f. 12 ; De Toni, Syll. Alg. 1889, 

 p. 954 ; West, Alg. X. Wales, 1890, p. 289 : Alo-. W. Ireland, 1892, 

 p. 147 ; Alo-. Eiig-1. Lake Distr. 1892, p. 725 ; Eoy & Biss. Scott. Desm. 

 1^94, p. 101; Xordst. Index Desm. 1896, p. 12l" ; West & G. S. West, 

 Wehv. Afric. Fresliw. Alg. 1897, p. 36 ; G. S. West, Alo-a-fl. Cambr. 

 1899, p. 217 ; West & G. S". West, Alg. X. Ireland, 1902, p. 34. 



Ursinella exigua Knntze, Kevis. gen. plant. 1881, p. 924. 



Cosmo. rium quadratulum (Gray) I) e Toni forma javanica GutAv. Alg. Ins. 

 Java, 1902, p. 590, t. 38, f. 31. 



Cells small, about twice as lono- as broad, fairly 





 deeply constricted, sinus somewhat open ; semicells 



subquadrate witli the angles rounded, sides and apex 

 almost straight or very slightly convex. Side view of 



~ O / 



semicell broadly elliptic. Vertical view elliptic, ratio 

 of axes about! : T4. Cell-wall smooth. Chloroplasts 

 axile, one in each semicell, each with a central pyrenoid. 



Zygospore unknown. 



Length 14'o-29/z; breadth 9'5-15/*; breadth of 

 isthmus 8-6 p. ; thickness 7-10 //,. 



EXGLAXD. Eisley Boo-, S. Lancashire (Roi/), Dela- 

 mere, Cheshire (Rot/), Chippenham Fen, Cambridge ! 



