436 BULLETIN OF THE BUREAU OF FISHERIES 



on the Halcyon cruise in 1920 and 1921; but, as pointed out above (p. 396), a com- 

 paratively rich collection of Chaetoceras was made in Ipswich Bay on January 30, 

 1913 (see also Bigelow, 1914a, p. 405). 



According to McMurrich (1917, and unpublished notes), the genus Chaetoceras 

 as a whole is scarcest at St. Andrews during the winter and most abundant between 

 mid-June and September. Fritz's (1921) more detailed counts of the several species 

 of Chaetoceras combined, at the same locality, show constantly increasing numbers 

 from the middle of March through April and May, with very abundant flowerings 

 in July and August followed by a decrease during the autumn to the midwinter 

 minimum, when the genus was so scarce that on two occasions (December 27 and 

 January 13) none at all were detected. 



McMurrich's, Bailey's (1915 and 1917), and Fritz's lists for St. Andrews, com- 

 bined, comprise the following species: Ch. boreale, Ch. constrictum, Ch. contortum, 

 Ch. convolutum, Ch. crinitum, Ch. criophilum, Ch. danicum, Ch. debile, Ch. decipiens, 

 Ch. diadema, Ch. laciniosum, Ch. sociale, Ch. teres, and Ch. willei. Ch. debile begins 

 flowering actively there in April and May, is far the most important species numeri- 

 cally, and was chiefly responsible for the very rich Chaetoceras flora of July and August 

 recorded by Fritz. Ch sociale, which yielded her next largest counts, was practically 

 nonexistent in November, December, January, February, and March; appeared in 

 April; flowered actively (207,500 per haul) in May; vanished in July; reappeared 

 in August; and attained its maximum abundance (280,000 per haul) on September 6. 

 Ch. diadema and Ch. laciniosum have been found at St. Andrews from late winter 

 through spring, summer, and early autumn, both of them having their plurimum in 

 July. Ch. decipiens has been found sparsely represented at St. Andrews in late 

 June, July, August, September, October, and early November, and the various other 

 species only between early July and the last week in October. The most notable 

 difference between the status of the genus Chaetoceras at St. Andrews, as contrasted 

 with the open gulf, is the scarcity of oceanic species. Ch. atlanticum and Ch. densum 

 have not been detected there at all. Fritz found C. criophilum in only one haul 

 on October 12 at St. Andrews. It is also interesting that in 1917 Ch. constrictum did 

 not appear in Fritz's lists at St. Andrews until July 17 — i. e., about a month later 

 in the season than on the other side of the Bay of Fundy in 1920 (p. 435). Fritz 

 (1921, p. 53) has remarked that the greatest number of species of Chaetoceras was 

 recorded for September, though the plurimum for the genus as a whole and for its 

 two most numerous species fell in August. Fish (1925) reports 20 species ofChae- 

 toceras at Woods Hole, but only two of them — decipiens and didymum — were plentiful 

 enough in his catches ever to be classed as "abundant." These two showed a suc- 

 cession of maxima in winter, summer, and autumn; not, however, in spring. 



Coscinodiscus 



The genus Conscinodiscus is very widely distributed in the Gulf of Maine, 

 both in time and space. In midwinter, on the whole, it is the dominant genus of 

 diatoms, both at St. Andrews (McMurrich, 1917; Fritz, 1921) and along the northern 

 and western shores of the gulf generally as off Cape Cod; for example, in Massa- 



