118 
BULLETIN OF THE BUKEAU OF FISHERIES 
species, proved to be the most conspicuous form (fig. 15). Later this was 
replaced by Leptocylindrus danicus and Slceletonema costatum. Both of these 
species are north temperate noritic 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 
• t • • • • 
rH bD fX -P > O 
;d <U O O OJ 
•-a -=35 CO O 23 <2j 
C*boreale 
C« contortion 
C«eoar eta turn 
Cadanictcn 
O.debile 
C^denstsn 
C.diadeioa 
C*didynmm 
C*lacxniosiim 
Ctlorenzianum 
C«peravianinn 
C.schuttii 
C*sociale 
C.willei 
Cmitra 
G»sp.nov. 
C.oriopliilum 
Cadeoipiens 
Fig. 21. — Distribution of Chsetoceros 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 hrightwelli, 
Til alas siothrix nitzscMoides, Rhizosolenia setigera, R. sJiruhsolei, and Chsetoceros 
sociale, all of which are neritic species (figs. 10, 11, etc.). Two oceanic forms 
