[bailey-mackay] diatoms FROM VANCOUVER ISLAND, B. C. 151 



II. Forms not Distinctly Planktonic. 



The forms here included are all to be found at times in plank- 

 tonic gatherings, but do not exhibit the same adaptations to flotation, 

 and are either attached to or sessile upon algae, or themselves exhibit 

 an algoid mode of growth. They are most abundant in shallow waters 

 and especially where these are freshened, as at the mouths of streams 

 or estuaries. Their preparation for study involves not only the remov- 

 al of salt but of algae, Crustacea, and infusoria as well, this being effec- 

 tively secured with sulphuric acid and potassium chlorate. The 

 cleaned material may then be mounted in styrax or balsam. 



COCCONEIS. 



This genus is very abundantly met with in the collections from 

 Vancouver Island, some gatherings containing little else. The species 

 are also remarkable for their variety and beauty. No less than eight- 

 een are enumerated as species in the appended list, although some are 

 considered on good authority to be but varietal forms. A few have 

 been noted provisionally as new species, and on fuller investigation 

 may prove to be but very divergent varieties. The difference between 

 the two valves of Coconeis and the evident range of variation in size 

 and sculpture account for the difficulties of the definite determination 

 of the species. 



C. scutellum Ehr. as usual is most abundant, being often found 

 clustered in very large numbers on the fronds of algae. As many as 

 nine varieties are noted some of which have figured as species by their 

 first describers. Dr. MacKay notes provisionally a species as possibly 

 new and of specific distinction. He notes under the name of C. 

 parallela a distinctive form of which at least six varieties have been 

 observed. The sculpture consists of dots in longitudinal rows parallel 

 to the longer axis, to some extent suggesting a Raphoneis. But the 

 2, 3 and 4-rowed varieties have forms with and without a sub-marginal 

 line or band which he thinks demonstrates them to be Cocconeis. 



C. Nanaimoensis and C. Fraseri are provisional names given to 

 two forms somewhat resembling Raphoneis Archeri O'M., the former 

 showing a fine sculpture along the ribs of more than 20 to 10 mi- 

 crons. Their relationship in valve sculpture and shape to C. costata 

 and C. pinnata suggested at first their cocconeoid character. 



C. dirtipta Greg, is not uncommon in some of the gatherings, as 

 in one of 20 fathoms; but it is wanting in others. The same is true 

 of C. interrupta Grun. Another form resembling C. dirupta also occurs 

 and may be only a variety; but while resembling it in size and the 

 division of its surface into quadrants, has the divisions, (instead of 

 being made by simple lines or narrow zones across the valves, with the 



