1913- No. 8. 



JAPANESE DIATOMS, 



5 



ScHRÖDKR mentions a form o( CJi. polygonum Schvit (vom Ja.pa.nese 

 material. The slight convexity of the valval surface, not only in this 

 species but also in many others, is always more pronounced in the broader 

 frustules, and becomes hardly recognizable as the frustules get narrower. 

 He also mentions C. skeleton Schutt from the same material. After a 

 careful study of an exhaustive material from A'arious parts of Japanese 

 seas, we are inclined to think that the different forms distinguished by 

 Schröder may be nothing more than various forms of Ch. atlanticmn 

 Clevk. He seems to have attached too much importance to the form of 

 the foramen. Both ('. polygonum forma and C. skeleton Schi-tt are 

 stated by him to have been poorly represented in his material, which 

 had been collected in October. The present species occurs in enormous 

 quantities about northern Japan during winter. 



Fig. 6", in OKA>rrHA's paper mentioned above should be rather 

 referred to C. neaptolitainim Schröder. 



Loc. Tosa; Kuriles (Okamura). Enoshima (Schröder), Volcano Bay; 

 Otaru Bay (Yexdo). 



Chaetoceras neapolitanum Schröder. 



Schröder: p. 29, PI. i, fig. 4. — Do,: 1906. p. 348, fig, 12, — 

 Gran: 1906, p. 65, fig. 76, 



^=C. atlanticum Okamura p. p. 1907, p. 89, PI. IV, figs. 57, 63, 

 Okamura had some hesitation in referring his specimen, delineated 

 by him as fig. 63, 1, c, to C. atlan- 

 ticum Cleve. It belongs undoubtedly 

 o the present species. He assigned 

 C. atlanticum Cleve to the sea off 

 the Kuriles as also to Tosa Prov. So 

 far as we could ascertain, the present 

 species seems to be limited to the 

 warmer seas, while C. atlanticum 

 Cleve occurs only in comparatively 

 colder seas. We have nevertheless 

 doubts about the localities he men- 

 tioned. 



That the present species is not a 

 narrow form of C. atlanticum Cleve 



Fig. 2. Chaetoceras iieapolitanitni 



Schröder. 

 Part of a chain, from water sam- 

 ples. The spines in the foramina, 

 and the spots in the setæ are in- 

 visible in the water preparations. 



X 520. 



