(4) 
(5) 
(6) 
(7) 
THE MICROPLANKTON OF PLYMOUTH SOUND. 165 
Centropages typicus Kroyer. Common in September and October, 
1915, scarce or absent through the winter, rather more abundant 
in May, becoming rare again in August. 
C. hamatus Lillj. Common in September and October, 1915, then 
absent until August, when it is very common on the 16th. 
Isias clavipes Boeck. Fairly common in May, rare in June. 
Temora longicornis Miiller. Very common all through the summer 
and in the middle of February, common in parts of November, 
but rather rare in winter. 
Anomalocera Patersoni Templeton. From September to the begin- 
ning of November ; not common. 
Labidocera Wollastoni Lubb. Not common, in July. 
Candacia armata Boeck. Rare through the winter, common in 
July and September. 
Parapontella brevicornis Lubb. Common in February and March 
and occasionally in May, otherwise rare; absent from October 
to February. 
Acartia clausii Giesbr. I find this species of Acartia the only one 
present in 1916. It is exceedingly abundant most of the vear, 
very common on and off from May to the beginning of January 
and very seldom absent altogether. 
Longipedia Scotti G. O. Sars. Once only in February. 
L. minor Scott. Once in water samples and once in the tow nets, 
June. 
Euterpina acutifrons (Dana). Rare, October to December. 
Idyca furcata Baird. Once only in December. 
Amphiascus similis Claus. Rare, September and October. 
Oithona similis Claus. More or less common throughout the year 
except from November to January. Very common in the middle 
of February and the middle of May. 
O. nana Grubb. Rare, January to May. 
O. plumifera Baird. Rare, from February to May, and im Sep- 
tember. 
Coryceus anglicus Lubb. Present most of the year, but rarest 
in the summer. Through October and November it agrees 
with Pseudocalanus in its abundance, but becomes scarce in 
December. 
NEW SERIES.—VOL XI. NO. 2. MAY, 1917. M 
