60 



WISCONSIN PHYTOPLANKTON 



var. uNCiNATUM De Brebisson. PI. 66, Fig. 4. 

 in Ralfs, Brit. Desm. 115, pi. 19, figs. 3D-3F. 1848. 



Cells larger, semicells broadly subpyramidate, lateral margins con- 

 cave between the angles, apex broadly truncate and plane ; spines at 

 polar and superior lateral angles suberect, generally slightly curved, 

 spines of basal angle curved and subparallel ; center of face of semicell 

 with a broad granulate area, the granules generally in an irregular 

 ring or ellipse. (Tychoplanktont.) 



Cells 75 fi long with spines, 60 ijl without spines ; 66 ix broad with 

 spines, 48 ix broad without spines ; isthmus 17.5 /x broad ; spines 8-10 n 

 long. 



Tank. (rrr). 



The erect curved spines, granulate central area and semicell shape 

 mark the points of difference between the variety and the type. The 

 granulation of the central area is exceedingly variable in both size 

 and number as well as in the arrangement of the granules. 



4. Xanthidium subhastiferum W. West. PI. 66, Figs. 5-12. 



Jour. Linn. Soe. Bot. 29: 166, pi. 22, fig. 4. 1892; W. & G. S. West, ibid. 35: 

 540, pi. 16, figs. 4-5. 1903; W. & G. S. West, Trans. Roy. Irish Acad. 33: 102, 

 pi. 11, figs. 13-15. 1906. 



Cells of medium size, length and breadth (without spines) equal, 

 very deeply constricted, sinus acute-angled, with apex acuminate and 

 outer margin widely open, isthmus narrow; semicells transversely 

 elliptic, curvature of ventral and dorsal margins about the same ; lat- 

 eral margins truncate-retuse, with two, long, fairly stout, somewhat 

 divergent, straight or slightly curved spines that lie in the same ver- 

 tical plane; semicell apices at times with a faint indication of a 

 truncate elevation in the median portion. Vertical view elliptic, poles 

 with two straight spines that lie in the same vertical plane, lateral 

 margins with wall thickened in the median portion. Lateral view of 

 semicells circular, with portion of wall above the isthmus thickened. 

 Cell wall finely punctate, without ornamentation in the thickened 

 portion of the cell face. Chloroplasts parietal, four in each semicell 

 and each with a single pyrenoid. ( Euplanktont. ) 



Zygospores unknown. 



Cells 41-73 jLt long with spines, 35-52 fi long without spines ; 

 60-101 fj. broad with spines, 35-52 ix broad without spines ; isthmus 

 9-14 fi broad ; thickness 23-25 fi ; spines 10-28 [x long. 



Adelaide (rrr). Bear (rr), Beaverdam (c), Birch (ss), Catherine (sss). Cat- 

 fish (sss). Cranberry (sss). Devils (rrr), Diamond (ss). Duck (rr), Dummy (rr), 

 Found (rrr). Half Moon (rrr). Horseshoe (s), Kawageusaga (rr), Lac du Flam- 

 beau (rrr), Mercer (ss). No Mans (ss), Rock (ss), Sanford (rrr). Shell (rr), 

 Sishebogema (ss). Squirrel (rr). Tamarack (rr), North Turtle (rr). 



There is considerable variation from the typical structure in this 

 species. One type of variation includes cells with supplementary 



