20 M ARINE AND FISHERIES 



5 GEORGE v., A. 1915 

 Fig. 12. Hyalodiscus subtilis — Bail. 



This species is not uncommon in plankton gatherings, both from the Bay of 

 Fundy and Gulf of St. Lawrence, but its representatives are usually much smaller 

 than those of the same species found at the more southern points on the Atlantic 

 sea-board. 



Fig. 13-14. Coscinodiscus — Ehr. 



This genus is more abundantly represented than any other, except perhaps 

 Chaetoceros, in the plankton flora of the Bay of Fundy as elsewhere. The species 

 most commonly met with are C. asteromphalus (Fig 13) of which C. oculus-iridis 

 is a variety, C. eccentricus-'EhY. (Fig. 14) and C. radiatus Grun, though quite a num- 

 ber of others have been observed. 



Fig. 15-16. Grammatophora. This can hardly be regarded as a true plank- 

 tonic genus, being usually, perhaps always, attached, and having a somewhat 

 littoral habitat. Yet scattered frustules and sometimes chains are not uncommon 

 in plankton gatherings. The species most commonly met with are G. marina 

 (Fig. 15) and G. serpentina (Fig 16) • 



Plate III. Fig 17. Synedra. 



The genus Synedra is not uncommon in planktonic gatherings, being well 

 adapted by its lengthened form to a life of flotation. This feature is most pro- 

 nounced in Synedra undulata, Bail, a species which, while rare in the waters of the 

 Bay of Fundy, is not very uncommon in those of the Gulf of St. Lawrence and 

 Prince Edward Island. In addition to its almost extravagant length it has the 

 further peculiarity, to which its name refers, of being corrugated or undulatory 

 through the larger part of that length, thus adding materially to its strength. 



Plate 3. Fig 18. Nitschia. 



This genus exhibits the same adaptation to flotation as the preceding genus, 

 the length being greatly disproportionate to its breadth. This is seen more or 

 less conspicuously in all the Nitschias, but is especially marked in N. longissima 

 (Fig 18) of which all but the central part is extremely narrow and spinous, the 

 total length, as in the figure, being often nearly twenty times its widest diameter. 



Plate III. Fig. 19. Biddulphia. 



This is eminently a planktonic genus, its representatives being found in 

 most tow-net gatherings. The individual frustules are provided with more or less 

 prominent horns, aiding flotation, but this is probably much more effectually 

 brought about by the adherence of the frustules in long chains, sometimes contain- 

 ing twenty or more individuals. The four species represented are B. aurita, 



