H. H. GRAN AND K. YENDO. 



M.-N. Kl. 



= C. dispar Castr. 1886: p. 76, PI. 8, fig. 6. 

 = C. compadum Schutt. 1895: p. 46, fig. 23. 

 = C. polygonum forma ScHiuioEH. 1906: p. 348, fig. 13. 

 = C. skeleton Schrödkr. 1906: p. 337. 

 The Japanese form of the present species presents a shght difference 

 from the Atlantic form. The terminal horns diverge at much wider 



Fig. I. Chaetoceras atlantiaim Cleve. 



a. Part of a chain. X 360. 



b. Smaller and elongated frustules. X 520. 



c. Compressed form found mixed with a. X 360. 

 All drawn from fresh specimens. 



angles in the former than in the latter. The angle formed b}^ the horns, 

 however, varies according to the size of the frustules. In the broader 

 forms the horns are more divergent, the angles between them measuring 

 about 120°; and in the narrower forms they are at first at about a right 

 angle, but very soon bend outwards. The setæ in the corresponding 

 positions are generally parallel to one another, and lie in the same plane. 

 Minute spots are found in the terminal horns, as in the Atlantic forms. 



