Marine Diatoms 29F 
Trigonium Cl. 
oe a discussion of the need for this genus see Mann, Diat. Alb. Voyages, 
p. 289. 
Trigonium arcticum (Bright.) Cl. 
Sch. Atlas, Pl. 79, figs. 5-7. 
This massive diatom is common in all arctic waters. An identical form, 
except in general of larger size, isequally common in the Antarctic; its name is 
unnecessarily changed to T. antarcticum. Found at Stations 41, 43a, 43b, 43c 
and 43g. 
Trigonium formosum (Bright.) Cl. 
Sch. Atlas, Pl. 79, figs. 2-3. 
To be held separate from the former. Found at Station 43c¢, scarce. 
Tropidoneis Cl. 
Tropidoneis elegans (W. Sm.) Cl. 
Greg. Diat. Clyde, Pl. 12, fig. 58; Perag. Diat. France, Pl. 41, figs. 2- 6. 
Found only at Station 43a, and scarce. 
Tropidoneis Lepidoptera (Greg.) Cl. 
Van Heurck Syn., Pl. 22, figs. 2-3; Perag. Diat. France, Pl. 39, figs. 1-9. 
Found at Stations 20b-c and 43c, scarce in both. 
Tropidoneis Stauroptera (Bail.) V. H 
Van Heurck Treat., p. 263; Cl. Arct. Diat., Pl. 3, fig. 13, misnamed; Greg. 
Diat. Clyde, Pl. 12, fig. 59c, misnamed. 
Cleve failed to see the fitness of his genus T'ropidoneis for this diatom and 
proposed the unnecessary new genus Pseudo-Amphiprora. Found at Stations 
23, 41, 48b and 48c; scarce in all. 
Smithsonian Institution, United States National Museum, Washington, D.C., 
May, 1925. 
