COSMARIUM. 267 



Owing to the close relationship which C. insequalipellicum 

 hears to C. retiisuiti we have given figures of the former for 

 the purpose of comparison (ride PI. XCI, figs. 4 and 5). 

 Schmidle (' Alg. aus Nyassa-See/ 1903, p. 68) has placed it 

 as " C. retusiforme var. insequalipellicum," but in this he has 

 made a decided error., as it is much more closely allied to 

 C. retnxiun, and might with justice be regarded as " C. retusnm 

 var. insequalipellicum nob." 



222. Cosmarium ovale Kalfs. 

 (PL XCII, fig. 1 ; Pi. XCIII, fig. 1 ; PI. XGIV, fig. 1.) 



Cosmarium ovale Ealfs, Brit. Desm. 1848, p. 98, t. 15, f. 9 [Ealfs in Ann. 

 Mag. Xat. Hist. 1844, p. 394, t. 11, f. 7, refers to several species of the 

 genus : Hass. Brit. Freshw. Alg. 1845, p. 366, t. 86, f. 8,, 9, = = copy of 

 Ealfs, 1844]; Kiitz. Spec. Alg. 1849, p. 175; Arch, in Pritch. Infus. 

 1861, p. 733; Lund. Desm. Stiec. 1871, p. 53 ; Delp. Desm. subalp. 1877, 

 p. 34, t. 10, f . 1-4 ; Kirchn. Alg. Schles. 1878, p. 146 ; Wolle, Desm. 

 U. S. 1884, p. 57, t. 13, f . 8-9 ; Cooke, Brit. Desm. 1887, p. 100, t. 38, f. 3 ; 

 West, Alg. W. Ireland, 1892, p. 164 ; Eoy & Biss. Scott. Desm. 1894, 

 p. 170; Nordst. Index Desm. 1896, p. 192; West & G. S. West, Alg. 

 S. England, 1897, p. 488; Alga-fl. Yorks. 1900, p. 82; Alg. N. Ireland, 

 1902, p. 37 ; Scott. Freshw. Plankton, I, 1903, p. 527 ; Further Contrib. 

 Plankton Scott. Lochs, 1905, p. 485; Comp. Study Plankton Irish 

 Lakes, 1906, p. 85 : Borge, Beitrage Alg. Schweden, 1906, p. 30. 



Cosmari'lii'Di ovale Hansg. Prodr. Algenfl. Bohm. 1888, p. 191, f. 113. 



Pleurotceniopsis (Cosmaridium) ovalis (Ealfs) De Toni, Syll. Alg. 1889, 

 p. 912. 



Cells very laro-e, 1-f-lf times as long as broad, 



9j CJ *-* J * -* 



deeply constricted, sinus narrowly linear with a slightly 

 dilated extremity ; semicells ovate from a broad, flat 

 base, the upper half considerably more attenuated 

 than the lower half, basal angles rounded, lower half 

 of sides convex, upper half almost straight, apex 

 rounded but always with an indication of being sub- 

 truncate, lateral margins furnished with 19-21 large 

 conical granules, and with a somewhat irregular series 

 within the margin, often with quite a number of these 

 large granules within the basal angles, margin of the 

 extreme apex usually smooth but with one or two 

 series of conical granules within. Side view of semi- 

 cell ovate from a broadly rounded base, apex rounded ; 

 grannies forming a broad band extending up the 

 middle from the isthmus to the apex (4-5 visible at 

 the apical margin), disposition of granules very 



