118 BULLETIN OF THE BUREAU OF FISHERIES 
species, proved to be the most conspicuous form (fig. 15). Later this was 
replaced by Leptocylindrus danicus and Skeletonema costatum. Both of these 
species are north temperate neritic forms, which are supposed by Ostenfeld 
to exist all the year round on the bottom, being carried up among the plankton 
in the flowering season and during high winds. The distribution at Wood Hole 
appears to substantiate this very well (figs. 10 and 11, p. 105). The winter flowering 
e » e @ e e 
co ta¥4) Qe + > tS) 
‘3 S ) S) e) o 
a) <= “A io) & (=) 
C.boreale 
Cecontortum 
Cecoarctatum 
Cedanicum 
Cedebile 
€edensum 
Cediadema 
C.didymum 
€elaciniosum 
C.lorenzianum 
Ceperuvianun 
Ceschuttii 
Cesociale 
Cewillei 
Cemitra 
C.spenov. 
Cecriophilum 
C.decipiens 
Fic. 21.—Distribution of Cheetoceros from June to December, 1922 
season is evident, and the scattered occurrence throughout the year can be best 
explained by Ostenfeld’s theory. Although very similar to tychopelagic forms, 
these two species differ in that they multiply greatly while members of the plankton. 
Other abundant members of the 1922-1923 winter society were Ditylium brightwelli, 
Thalassiothrix nitzschioides, Rhizosolenia setigera, R. shrubsolei, and Chetoceros 
sociale, all of which are neritic species (figs. 10, 11, etc.). Two oceanic forms 
