COSMARLUM. 13 



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136. Cosmarium quadridentatum West & Gr. S. West. 



(PI. XCIII, fig. 5.) 



Cosmarium quadridentatum West & G. S. West, Alg. N. Ireland, 1902, 

 p. 36, t. 2, f. 11. 



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

 stricted, sinus sublinear, slightly open outwards, and a 

 little dilated at the extremity; semicells trapeziform- 

 semicircular, basal angles produced into a prominent 

 acute tooth, sides slightly triundulate, apex broad and 

 almost straight, with three indistinct granules within 

 each lateral margin. Side view of semicell ovate from 

 a broad base, apex truncate ly rounded. Vertical 

 view elliptic, with acute poles, ratio of axes about 

 1 : 1'S. Cell-wall smooth except for the submarginal 

 granules. Chloroplasts axile, one in each semicell, 

 with a central pyrenoid. 



Zygospore unknown. 



Length 23 '4-2 5 /x; breadth (with the basal teeth) 

 23-24^, without the teeth 21 p; breadth of isthmus 

 8*0/1; thickness 12 p.. 



IRELAND.- -Loughs Fadda and Gratny, and near 

 Louoii Grlentornan, Donegal ! 



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This characteristic species occurred in abundance in Lough 

 Gratny, but was somewhat scarce in the other localities. 



137. Cosmarium Corriense Bissett. 

 (PI. LXXVI, fig. 1.) ' 



Cosmarium Corriense Bissett in Roy & Biss. Scott. Desm. 1894, p. 44, t. 2, 

 f . 6 ; Nbrd'st. Index Desm. 1896, p. 84. 



Cells rather under medium size, about 1J times as 



lono- as broad, with a fairly deep constriction, sinus 



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somewhat linear but open along its entire length ; 



semicells trapeziform-semicircular, basal angles rect- 

 angular and scarcely rounded, upper angles broadly 

 rounded. Cell-wall finely granulate, granules arranged 

 in about 11 vertical series, about 22 showing along 

 the margin of each semicell. Side view of semicell 



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