148 MARIE V. LEBOUR. 
(30) C. boreale Bail. Chiefly in two nettings, Occasionally in spring and 
early autumn. 
(31) C. decipiens Cleve. Fairly common in spring and summer. rare in 
autumn and winter. 
(32) C. teres Cleve. Chiefly in February and March, common in March. 
(33) C. contortum Schiitt. Occasionally in July, August and September. 
(34) C. didymum Ehr. Begins in February and continues through the 
spring and summer until October. Very common in August. 
500 
CHAETOCERAS SPECIES 
400 
300 
200 
100; 
SEPT. OCT. NOV. DEC. JAN, FEB. MAR. APR. MAY JUNE JULY AUG. SEPT 
1915 1916 
Fic. 5.—Curve showing the average number of Chetoceras in 50 cc. for each month, 
(35) C. constrictum Gran. One of the commonest species from July to 
the end of September with its maximum in May when it suddenly 
appeared and disappeared. Resting spores noticed commonly in 
August forming in the chains. At all depths, but the largest 
numbers nearly always at the surface. 
C. Willec Gran. Rare from June to October. 
C. breve Schiitt. Rare in August. This is recorded often by Gough. 
C. laciniosum Schiitt. Occasionally from June to October. 
C. diadema (Ehr.). Only seen once in August. 
C. pseudocrinitum Ostenf. Common in May and June, at other 
times rare. At all depths. 
(41) C. curvisetum Cleve. The commonest species of Chetoceras : begin- 
ning in March it continues throughout the summer till the middle 
of September, Maximum of 37 per ce. at the end of May. This 
is certainly the most important species of Chetoceras here and 
helps greatly to swell the diatom maximum both in May and 
August. Largest number at the surface, although it occurs at 
all depths. 
