980. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
different set of species from those that predominated a 
mouth before. The April Diatom maximum is formed 
in the main by species of Chaetoceras (C. decipiens, 
C. teres, C. debile, C. sociale and C. diadema) and 
Lauderia borealis, while that in June is caused by 
Rhizosolenia semispina, R. shrubsoli and Guinardia 
flaccida. In September the April Diatoms reappear to 
some extent, especially Chaetoceras debile, C. decipiens, 
C’. teres, and to a less extent C. densum. Lauderia 
borealis is also present, but Chaetoceras sociale and 
C. diadema are practically absent in September. In 
fig. 4 we give curves fot the distribution of these 
Abril 
8 millions 
Vv 
3 
= 
Vv 
a) = : 
0 | Mebnty 
~ ney 
v Car 
d ci \ 
as gl 
6 ay y! 4 
;! 1 
vi H 
Qo! ‘ 
Ny \ 
<c} 4 
Ri ¥ 
4 ' 
( ‘ 
t \ 
' ' 
t ' 
: Fia. 4 
4 
H \ 
\ 
: \ 
D 
! 1 
; ' 
i} 
! tN ' 
! aN ' 
' Ho 1 
U f] ‘ : 
1 
ee ke 
‘ 
oe. ' : d . \ 
d bts \ 
i~ i Tees : ' 
t 
' J re H \ 
ny A hed \ H 
: 3 : : \ 
| million oy ! H : \ 
i ' i \ \ 
' 2 aN Chaetoceras 
‘ 

Jan. 
——— 
Feb. Mar. Apr. May June July Aug. Sept. Oot. Nov. Dec. 

