COSMARIUM. 255 



crenate than in C. speciosum and allied species, and the crena- 

 tioiis are slightly emarginate. The row of short vertically dis- 

 posed ribs across the base of the semicells is also a distinctive 

 feature., as each outstanding rib is quite smooth. 



214. Cosmarium subalatum West & G-. S. West. 



(PI. XC, figs. 1-3.) 



Cosmarium subalatum West & Gr S. West, Alg. Madag. 1895, p. 63, t. 7, 



f. 31 ; Nordst. Index Desm. 1896, p. 243 ; West & G. S. West, Alg. 



Burma, 1908, p. 207. 

 C. alatum as recorded by West & Gf. S. West, Welw. Afric. Freshw. Alg. 



1897, p. 122; Alg. S. England, 1897, p. 489; Alga-fl. Yorks. 1900, p. 87. 



[Not C. alatum Kirchn. 1878.] 



Cells small, 1^-lJ times as long as broad, deeply 

 constricted, sinus narrowly linear with a slightly 

 dilated extremity; semicells widely truncate-pyrami- 

 date, sides 3-crenate (including the rounded basal and 

 apical angles), crenations of equal size, or the basal one 

 very slightly larger than the median and apical crena- 

 tions, apex truncate and 4-crenate (including the apical 

 angles), the two crenations between the apical angles 

 considerably smaller than the angles themselves, all the 

 crenations bigranulate except the basal ones which are 

 trigranulate ; within the margin minutely granulate, 

 granules in radiating and subconcentric series, usually 

 binate just within the crenations ; in the centre with a 

 rounded granulate tumour, 7-8 granules disposed in a 

 circle around a central one. Side view of semicell 

 ovate, tumid at the base on each side, apex rounded or 

 rounded- truncate. Vertical view elliptic, with a small 

 3 -granulate tumour at the middle on each side, granules 

 arranged in 10 transverse series. Chloroplasts axile, 

 one in each semicell, with a single pyrenoid. 



Zygospore unknown. 



Length 18-24 [JL; breadth 14'5-21/x; breadth of 

 isthmus 3 '8-6 '5 p. ; thickness 10' 5-11 ^. 



ENGLAND.- -Boston Spa, W. Yorks ! Pilmoor, X. 

 Yorks ! Slap ton Sands, Devonshire ! 



Geoyr. Distribution.- -Central Africa. Madagascar. 

 Burma. 



