[bailey-mackay] diatoms FROM VANCOUVER ISLAND, B. C. 143 



size both of the chains and individual frustules, partly by the form of 

 the interspaces separating the frustules, which vary with the seasons 

 from that of narrow ellipses almost to circles, and lastly by the charac- 

 ter of the bristles which proceed from the angles of the cells, and con- 

 trast both in direction and size with the terminal bristles. All the 

 bristles are smooth. Ch. Peruvianum, Ch. boréale and Ch. criophyllum 

 are also large species with stout rigid spines, those of the two last being 

 also strongly imbricated. Ch. didymum Ehr. is a fairly large species 

 distinguished by the presence of small conical processes in the middle 

 of the surfaces of the contiguous cells. Ch. paradoxum CI. is most 

 readily recognized by its resting spore known as Syndendrium diadema 

 Ehr. when these are present, the convex surface of the valve being 

 adorned with somewhat numerous processes, suggesting the specific 

 name of the spore. 



Ch. crinitum Schiitt, as its name implies, is thickly beset with long 

 flexible hairs. This is also the case with Ch. sociale Lauder, of which 

 two varieties occur, one with the small irregular cells closely united 

 to form a more or less curved, crescentic, sometimes almost circular 

 chain, with the bristles for the most part extending outwardly from 

 the latter, while the second is not circular but presents rather the 

 appearance of an umbelliferous flower cluster, one bristle of each cell 

 being greatly elongated and so placed as to form with the similar 

 bristles of other cells a sort of stalk or stem supporting the group, while 

 the remaining bristles are short and diverge from each other. Both 

 varieties are rather rare. Ch. saltans CI, and Ch. suhtilis CI. also 

 occur. Ch. dichaeta Ehr. was observed by Kendall. 



SKELETONEMA. 



This genus, which is readily recognizable by its lattice-like struc- 

 ture, is extremely abundant in most of the collections from the vicinity 

 of Departure Bay. It probably embraces several species but only 

 one, Skel. costatum, has been clearly distinguished. Chains of fifty 

 or more cells are of frequent occurrence and exhibit considerable 

 variety in diameter as well as in the intervals separating the individual 

 frustules. 



THALASSIOSIRA. 



Two species of this genus, Th. decipiens Grun. and Th. Norden- 

 skioldii Cleve are very common in the collections from Vancouver 

 Island, the former being characterized by the wide separation of the 

 frustules with a corresponding length of the slime-string which holds 

 them together, the engine-turned sculpture of the valve and the crown 

 of bristles bordering the latter; while the second species has the 

 frustules more closely approximated, lacks the engine-turned aspect, 



