Organic Siliceous Remains. 241 



77. S. bi«eriata, Breb. 



78. S. bifrons, Ktz. 



79. S. turgida W. Sm. 



80. S. linearis var. constricta, W. Sm. 



81. S. slevicensis, Grun. 



82. S. elegans, Ehr. 



83. S. tenera, Greg. 



84. S. cardinalis, Kitton. 



85. Nitzschia amphioxys, Ehr. 



86. N. elongata, Grun. 



87. N. speotabilis, Ralfs (?) 



88. N. sigmoid* a, Nitzsch. 



89. Stenopterobia anceps, Breb. 



90. Fragillaria construens, Grun. 



91. " " war. binodis, 6rr«n. 



92. F. capucina, Desm. 



93. F. undata, W. Sm. 



94. Synedra ulna, Ehr. 



95. Meridion circulare, Ag. 



96. Tabellaria floculosa, Roth. 



97. T. fenestrata, Lyngb. 



98. Cyclotella oparculata, ^4a. 



99. C. comta var. affinis, Grun* 



100. Melosira distans, Ehr. 



101. M. arenaria, Moor. 



102. M. orichalcea, Mertens. 



103. M. granulata, 2£Ar. 



104. M. crenulata var. valida, Grun. 



This list is not exhaustive of all the forms found in any given 

 locality, much less of all the species in the lacustrine deposits of 

 the province. Until the species have been more fully determined 

 in the whole range of deposits there will be little use in attempt- 

 ing to compare the forms of the lower deposits with those of the 

 upper or more modern. Great variations are observed in many 

 species of the diatomaceae, concomitant with their stage of develop- 

 ment, and also probably with their different environments. The 

 conditions of environment also affect their distribution. It is 

 remarkable in the Nova Scotian species, so far as observed, that 

 while most of the forms determined are also found in the dis- 

 tant waters of the Alps and the Jura, some of the deposits taken 

 from lakes but a few miles apart can be distinguished by the pre- 

 sence or absence of certain forms or by their relative abundance. 



16 



