1913- No. 8, JAPANESE DIATOMS. I 5 



The resting-spores have palhsade-spines on the marghis of both the 

 primary and the secondary valve. The primary valve is almost hemis- 

 pherical, and has numerous short spines over its whole surface; the 

 secondary valve is nearly similar, but is somewhat humped and has 

 short spines condensed about the summit. 



Log. Misumi (Yenuo). Hong Kong (Lauder). 



Sect. 8. Stenocincta Osten p. 

 Chaetoceras afßne Lauder. 



Lauder: 1864, p. 68, PI. 8, fig. 5. — Okamura: 1907, p. 96, 

 PI. 3, figs. 4, 5 (excl. 4 c). 



= C. Ralfsii Cleve: 1873 b, p. 10, PI. 3, fig. 15. — Osten- 

 feld: 1902, p. 238. — Karsten: 1905, p. 168, Taf. 31, fig. 8, 

 Taf. 33, figs. 16 — 18. — Schröder: 1906, p. 352. — Okamura: 

 1907, p. 97. 



= C. Schiittii Cleve: 1894, p. 14, PI. i, fig. i. — Gran: 

 1897 a, p. 19, PI. 2, figs. 19, 20. — Do.: 1905, p. 81, fig. 97. — 

 Schröder: 1906, p. 337. — Meunier: 1910, p. 236, PI. XXVI, 

 figs. 32—35- 



= C. sp. indet. Schutt: 1888, Taf. 3, figs. 2, 3. 

 = C. disticJium Schutt: 1895, P- 37' ^S- 2, a — b. 

 = C. angulatum Schutt: 1895, p. 37, fig. i, a — d. 

 = C. 2)f'oceruni Schutt: 1895, p. 38, fig. 3, a — b. 

 = C. javanicum Cleve: 1873 b, p. 10, PI. 2, fig. 13. — Do.: 

 1902, p. 19, p. 55. — Ostenfeld: 1902, p. 236, figs. 14, 15. — 

 Okamura: 1907, p. 96, PI. IV, fig. 55. 

 Chaetoceras affine Lauder is a widely-distributed species in the 

 warmer part of the Atlantic, Indian and Pacific Oceans. It is extremely 

 variable in its form, according to the conditions of the water which it 

 inhabits. In the Japanese waters two types occur. The first form has 

 rectangular frustules, their width generally greater than their height, and 

 narrow girdle-band wMth parallel suture- lines. The terminal horns are at 

 first patent and then bend upwards in a subulate manner, and lie in one 

 plane. They are armed with minute processes arranged spirally. The 

 second form has narrow, subcylindrical frustules, their height greater than 

 their breadth, and with roundish foramina. The terminal horns are less 

 curved and less divergent, rather acute, bent out of the apical plane. 

 They are not spinulated, but are densely beset with minute elevations dispo- 

 sed spirally. These two forms, however, are united by numerous intermediate 

 ones, so that no sharp boundary can be drawn between them. The At- 

 lantic forms approach more to the narrow one in general appearance, 



