[bailey-mackay] diatoms FROM VANCOUVER ISLAND, B. C. 149 



AMPHIPRORA, 



Four species of this beautiful genus have been observed, A. 

 alata Ktz. and A. sulcata O'Meara belonging to the group with com- 

 plex zones and sigmoid keels; and the following with simple zones by 

 some authors segregated into the genus Tropidoneis Cleve, viz.: 

 A. lepidoptera Greg, with a var. prohoscidea C, and A. maxima 

 Greg. var. gracilis Grun. Owing to the slight silicification of some of 

 these species and their consequent transparency they are not always 

 easily seen. 



AMPHORA. 



Not less than nineteen species of this genus appears to have been 

 observed as indicated in the sequel. Of these probably A. ovalis 

 Ktz. with its varieties is the most common. Besides those listed an 

 additional form has been observed which resembles A. exserta Gran 

 of Campeachy Bay. But it has a different striation, while another 

 resembles ^. angularis Greg having similar sinuous borders constricted 

 in the middle and with similarly produced ends. It may possibly be 

 A. laevissime Greg. There have been observed and noted several 

 other forms which could not be relegated to any of the species in the 

 list given at the end of this paper. 



THALASSIOTHRIX. 



This genus appears to be quite abundantly represented in the 

 plankton gatherings of Vancouver Island. Its zigzag chains often 

 embrace a considerable number of individual frustules of variable 

 length and breadth. To the writer they seem to correspond quite 

 nearly to Th. nitzschioides Grun. But in the list prepared by Dr. 

 MacKay who has seen only prepared mounts, the only species given 

 under this genus is Th. Frauenfeldii Grun. (following Peragallo). 

 The genus Thalassiothrix Cleve et Grunow is limited to the hair-like 

 forms with the more or less serrate edges. The form described first 

 above is in Dr. MacKay's list Thalassionema nitzschioides Grun, 

 with a sculpture on the edges of from 7 to 8 in 10 microns instead of 

 10 to 12. It therefore approximates the varieties Javanica Grun. 

 or lanceolata Grun. rather than the type species which has also been 

 noted by him. The separation of the older Thalassiothrix into two 

 genera, giving the linear or lanceolate forms so often connected in 

 zigzag to the genus Thalassionema, is a very appropriate amendment. 



FRAGILLARIA. 



Representatives of this genus in the form of long bands or ribbons 

 embracing many individuals and of various sizes are common in the 



Sec. IV, 1915—10 



