[bailey-mackay] diatoms FROM VANCOUVER ISLAND, B. C. 153 



SURIRELLA. 



This genus does not appear to be very abundantly represented 

 in the diatom flora of Vancouver Island, but nevertheless a con- 

 siderable number of distinct forms, some of which are quite large, 

 have been observed. S. lata Sm., 5. fastuosa Ehr. and 5. ovata Ktz. 

 have been noted together with a form related to lata, and coming close 

 to S. Japonica AS. as indicated in the general list. Other forms seen 

 have not yet been determined. They are found chiefly in connexion 

 with algae or in bottom muds, and in some circumstances are not easily 

 distinguished from forms of Campylodiscus or Cocconeis. 



NAVICULA. 



This prolific genus is represented in the Vancouver waters by 

 not less than 47 species, many of which, however, are inconspicuous 

 or of rare occurrence. The complete list is given at the end of the 

 paper. One of the larger species is N. Lyra Ehr. and its conspecies, 

 N. didyma or its relatives has been noted, as well as N. elliptica Ktz, 

 and N. humer osa Bréb. and N. viridis Ktz. Several varieties of 

 N. Smithii have been observed, some of which are ver}^ common. 

 N. aspera is listed under the genus Trachyneis Cleve, and is widely 

 distributed in at least four varieties. 



PLEUROSIGMA. 



This genus which Cleve subdivided into the Pleurosigma proper 

 and the Gyrosigma (in which the scupture lines cut at right angles) 

 is represented by at least nine species, three of which, Balticum, 

 decorum, and intermedium, are well known and widely distributed forms 

 PI. Olympianum Terry, first discovered in Puget Sound in view of the 

 Olympian range of mountains, resembles PI. Balticum Sm. in size and 

 general appearance, but difi^ers in being gradually but markedly con- 

 stricted towards the centre and has oblique instead of rectangular 

 striation. PI. fasciola Sm. is also common. 



SYNEDRA. 



This genus is represented by about ten species. Some of them 

 dififer from the described forms to such an extent as to suggest that 

 they may be new. Three of these will be found in the general list 

 at the end with notes pointing out the differences which characterize 

 them. Among the most frequently occurring forms is S. affinis Ktz. 

 of which there may be several varieties, the most abundant being var, 

 tabulata Grun. It is possible that a variety of this species may some- 



