COSMAIMUM. 65 



85. Cosmarium pseudoexiguum Racib. 

 (PL LXX, figs. 25, 26.) 



Cosma-rium (Pleurotseniopsis) pseudoexiguum Eacib. Nonu. Desm. Pol<>n. 

 1885, p. 71, t. 10, f. S fin descrip. of plate " C. sulexiguum"^ ; X<.rd<t' 

 Index Desm. 1896, p. 208; West & GK S. West, Alg. N. Ireland, 19UL>, 

 p. 34 ; Freshw. Alg. Ceylon, 1902, p. 166 ; Freshw. Alg. Orkneys and 

 iShetlands, 1905, p. 22. 



Pleurotseniopsis pseudoexigua (Eacib.) Lagerh. Algol. Bidr. II, 1887, p. I'.iv 

 Cosmaridium pseudoexiguum (Eacib.) Hansg. Prodr. Algeiifl. Bohm. 1*^. 

 p. 246 fin note]. 



Cells small, rather more than twice as long as broad, 

 very deeply constricted, sinus narrowly linear with a 

 dilated extremity; semicells snbquadrate (longitudi- 

 nally subrectangular), basal angles slightly rounded, 

 sides slightly convex, upper angles broadly rounded, 

 apex generally slightly convex, rarely straight or verv 

 faintly retuse. Side view of semicell subelliptic. 

 Vertical view elliptic, ratio of axes 1 : 1/6. Cell- wall 

 smooth. Chloroplasts parietal. 



Zygospore unknown. 



Length 19-25*7 (JL ; breadth 7-13*6 /A ; breadth of 

 isthmus 3 '8 4 JJL ; thickness 5-8*5 //,. 



WALES.- -Moel Siabod, Carnarvonshire ! 



SCOTLAND.- -Rhiconich, Sutherland ! Xear Lerwick. 

 Shetlands ! 



IRELAND.- -Errigal, near Glenties, and Sproule's 

 Louo'h, Doneo-al ! Louo'li Fea, Londonderry ! Shan- 



O O O e/ 



slieve, Down ! 



Geogr. Distribution. Gralicia in Austria. Poland. 

 Ceylon. Porto Eico. 



t/ 



This tiny species differs from C. exiguum Arch, in its rela- 

 tively greater length, its much deeper constriction, its closed 

 sinus, and in the possession of parietal chloroplasts. Although 

 we have obtained this species from several localities we have 

 not yet examined any living specimens,, and we have not been 

 able to satisfactorily make out the disposition of the chloi-"- 

 plasts, which were described by Kaciborski as parietal. 



Var. angustatum var. nov. (PI. LXX, fig. 27.) 



C. pseudoexiguum Eacib. fornia in West & G. S. West, Alga-fl. Yorks. 

 1900, p. 91. 



VOL. III. ^ 



