Tlie Diatoms of Nebraska 6i 



1 8. Mastigloia 



Mastigloia Thwaites in W. Sm. Brit. Diat., II, p. 64. 1856. 



Etym., Gr. /xaaro?, breast, and yXoios, gelatinous, from the 

 form of the mass in which it grows. 



Cells naviculoid with transverse septa between the valve and the 

 girdle ; septa on the margins forming regularly arranged compart- 

 ments, leaving an oval or linear space in the middle of the valve. 

 In girdle view the compartments appear as a row of coarse dots. 

 Valves symmetrical, ends attenuate, capitate, or cuneate ; striations 

 fine, granular. Chromatophores double, lying next to the valves, 

 deeply constricted in the middle or consisting of four plates which 

 lie either next to the valves or the girdle, but are not united at 

 the ends. 



A. Marginal cells arranged in a curved row. i. M. smithii. 

 AA. Marginal cells arranged in a straight row. 



b. Striations consisting of fine dots. 2. M. clliptica. 



bb. Striations consisting of coarse dots. 3. M. grcvillci. 



1. Mastigloia smithii Thwaites in W. Sm. Brit. Diat., II, p. 6$, 



pi- 54> fig- 341- 1S56. 



PI. 5, fig. 170. 



Lanceolate, more or less rostrate, or sometimes rostrate-capitate, 

 27-53 ju, long, 10-15 yu, wide; striations radiate, consisting of dots 

 arranged in longitudinal rows, 12-18 in 10 /x,, longitudinal rows 

 closer ; shortened, leaving a small round or rectangular space in 

 the center; marginal cells 5-8 in lO/t, arranged in a curved row, 

 not extending to the ends of the cell. 



In fresh water, Court Lake near Devils Lake, N. Dak. 



2. Mastigloia elliptica (Ag.) Schonf. Siisszv. FL, p. 63. 1913. 

 Frustulia elliptica Ag. in Kiitz. Syn. Diat., p. 10. 1833. 

 Mastigloia dansei Thw. in W. Sm. Brit. Diat., p. 64, pi. 62, 



fig. 388. 1856. 



PI. 5, figs. 171-175- 



Elliptical or linear-elliptical, 22-51 ^u, long, 10-18/A wide; ends 

 rounded, slightly constricted or cuneate; striations granular, radi- 

 ate, 15-20 in 10 /A, slightly curved, the middle ones alternately 

 longer and shorter; marginal rows of cells about 8 in lO/*,, not 



