12 



H. H. GRAN AND K. YENDO, 



M.-N. Kl. 



Sect. 6. Protaherantia. Ostenp. 

 Chaetoceras didymum Ehr. 



Ehrenberg: 1845^ P- -I5- — Rrightwell: 1856, PI. 7, figs. 

 3 — 7. — Cleve: 1889, p. 14, PI. I, fig.s. 3 & 4. — Gran: 1906, 

 p. 79, fig. 94. — Schröder: 1906, p. 337. — Okamura: 1907, 

 p. 95, PI. 4, figs. 44 -48 (excl. 45 a). 



= C. mamillanum Cleve: 1889, p. 55. 



= C ■ protuberans Schutt: in Apstein: 1901, p. 41. 

 var. gemiina Gran. 



Gran: 1906, p. 79, fig. 94. — Okamura: 1907, p. 95, PL 4, 



fig. 48 a— c. 



var. anglica Gran. 



Okamura: 1907, p. 95, PI- 4. 



Gran: 1906, p. 80, fig. 95. 

 figs. 44 - 47 (excl. fig. 45 a). 



= C. furcellatum var. anglica Grunow: in Van Herrck: 

 1S80-85, PI- 82, fig. 3. 



= C. didymum var. longicruris Cleve : 1 897 a, p. 2 1 , PI. i . fig. 1 1 . 

 = C. longicrure Ostenfeld et Schmidt: 1901, p. 154« — 

 Ostenfeld: 1903, p. 576. 



= C. arigliciiin Ostenfeld: 1902, p. 233. — Schröder: 

 19 o, p. 337. V2ir. protid)erans nom. nov. 



= G. protuherans Lauder: 1864, p. 79, PI. 8, fig. 11. — 

 Yendo: 1905, p. 45, fig. 16. 



= C. didymum Okamura: 1907, p. 95, pi. 4, 45 a (non alior). 



CJtaetoceras protuherans Lauder, if our determination is correct, 



resembles in many points G. didymum Ehr. The former may be 



distinguished by having the 

 setæ lying in one plane, and 

 the terminal horns more widely 

 divergent than in the latter. 

 These distinctions, however, are 

 not so clearly marked in the 

 material from the warmer seas, 

 where transitions may be found. 

 Until a more extensive material 

 has been studied therefore, we 

 think it right to keep Ch. pro- 

 tuberans as a variety of Ch. 

 '^^-^^ " didymum. 



b In the material from North- 



Fig. 5. Chaetoceras didymum Ehr. var. pro- grn Japan we find exclusively 

 tiiberaus. 

 . ,. r , • ,^ ■ , r var. protuberans while in that 



a. A portion of a chain. Material from -^ 



Misaki. X 360. from the southern part, the three 



b. Valval view of a frustule. X 360. varieties were found together. 



