14 



Dansk Botanisk Arkiv, Bd. 2, Nr. 4. 



Fig. 7. Coscinodiscus Jonesianus (Grev.) 

 nob., a, valvar view showing the position 

 of two big processes, the small snbmarginal 

 apicnli, the very small apiculi halfway to 

 the centre and the central rosette of ar- 

 eoles; b, valvar view showing a sector with 

 chromatophores and the nucleus. (&%&). 



lensis Ostf., C. biconicus Van Breemen, C. centralis Ehbg. and C. con- 

 cinnus Ehbg. Another species belonging hereto was rather common 

 in Dr. Justesens sample (fig. 7). On closer examination of the 



older literature I found that 

 it could be identified with 

 Eiipodiscus Jonesianus Greville; 

 at the same time it became 

 evident that C. biconicus Van 

 Breemen was the same as 

 Eiipodiscus ? vel Coscinodiscus 

 commiitatiis Grunow (1. c, p. 79). 

 Greville's description of his 

 Eiipodiscus Jonesianus (1. c, 

 p. 22) is not very good, but 

 on comparing it with the figure, 

 no doubt remains that we have 

 here a Coscinodiscus, as also 

 Van Heurck (1. c.) has pointed 

 out. The figure show r s three 

 large apiculi (processes) instead 

 of two, but it is probably an 

 error in drawing. Greville says 

 that the structure is »minute«, 

 and that ^the puncta in the 

 centre of the disc are rather 

 larger than the rest.« This makes it difficult to identify his species 

 with Grunow's C. commutatus as Van Heurck (1. c.) and Rattray 

 (Proc. Roy. Soc. Edinburgh, 16, 1888-89, p. 84) have done. Grunow 

 (1. c.) says : »Mit C. concinnus hängt eine bisher verwechselte und 

 übersehene, nicht seltene Art zusammen, welche ich Eupodiscus ? 

 commutatus genannt habe, welche aber vielleicht besser bei Cosci- 

 nodiscus bleibt. Sie kommt bei Cuxhafen, Brasilien, China, Java 

 und im Peru Guano vor und hat zwei kleine marginale Anhängsel . . 

 Die kleinen Anhängsel von C. commutatus stehen nicht diametral 

 gegenüber. Am Rande stehen kurze Stacheln, von denen, wie bei 

 C. concinnus, kurze, oft schwer sichtbare Radien nach innen gehen,« 

 He quotes A. Schmidt, Atlas, pl. 60, fig. 16, which represents a 

 specimen from Peru Guano, but which is fragmentary and unsatis- 

 factory. Quite recently we have got an excellent photograph of the 

 Cuxhaven C. commutatus in a paper by Chr. Brockmann (Brack- 

 wasserstudien, in Schriften des Vereins für Naturk. an der Unter- 

 weser IV, Geestemünde, 1914, p. 43, fig. 5). From this it becomes 

 evident that it is the same species as that described as C. biconicus 

 by Van Breemen (Plankton van Noordzee en Zuiderzee. Leiden 1905, 

 p. 23, cfr. Ostenfeld, Aral Sea, p. 148, pl. 6, figs. 1—3) from the 

 Zuyder Zee. 



This species is closely related to that from our sample, but it 

 differs in the much coarser structure and in the absence of the very 

 small apiculi halfway between the margin and the centre. Therefore 



