SPECIES OF DESMIDS. 89 



///. Cell nearly as long as broad; semi-cells rhomboid, sides all 



equal; sinus deep, wide rhombusoides.** 



n. Ends rounded; semi-cell subcircular, sinus a mere notch, 



globosum, 60 



/z. " " semi-cell subsemicircular (o). 



n. " " semi-cell oval (r), 



n. " " semi-cell elliptical, or hexagonal-elliptical; cell -J- 



longer than wide; diam. 25-42/4, sexangularc, 63 



n. Ends rounded semi-cell elliptical; cell ^ longer than wide; diam, 



2526/4 microsphinctum** 



n. Ends truncate; semi-cell hexagonal; diameter 12 1 00 in. (21/4) or 



less, polygonum, 65 



n. Ends truncate; semi-cell triangular; diameter -yj-^- in. (50/1) or less. 



galeritum, 70- 



n. " semi-cell subsemicircular, smooth; sinus deep, nar- 



row . . . nitidulum, 62 \psendonitidulum, 62 



n. " " " punctate or granular; si- 

 nus narrow lobulatulum* 



o. Sinus deep, narrow (/). 



o. Sinus deep, wide, almost linear; cytioderm smooth, sejunctum, 62- 



o. " rounded or oval; semi-cells lunately curved; cytioderm 



punctate lunatum, 65 



o. Sinus deep, wide, obtuse; semi-cells widening froirTa narrow base r 



infl&tuin* 

 o. Sinus acute angled, enlarging outwardly, rarely linear, 



pcrforatum* 



p. Cell elliptical; basal angles acute Baileyi, 64 



/. Cell suborbicular; basal angles obtuse; diameter -^-^ to T ^ in. 



(6o-ioo//), Ralfsii, 69. 



/. " " diameter ^ to ^ in. 



(30-38), constrictum, 58 



r. Cytioderm centrally somewhat granular; nucleus i in each semi- 

 cell, tumidum, 61 



r. " smooth or punctate; cells small, 



biotulatum, 60; tinctum, 61 

 s. Ends rounded; semi-cells semi-orbicular; crenae usually 9, 



undulatum, 67 



J. " " semi-cells subsemicircular; margins finely crenulate- 

 dentate Wolleannm* 



* Journ. R. Micr. Soc., Dec., 1885. f Journ. R. Micr. Soc., Feb., 1886. 

 ** F. W. Algse, p. 27 et seq. 



