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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



deposit was formed almost wholly of enormous numbers 

 of a very active little Peridinian or DinofLagellate of a 

 bright yellow colour (figs. 23 and 24). More careful 

 investigation, in which Mr. Eiddell and Miss M. 

 Latarche helped me, enabled us to identify this form as 

 Amphidinium operculatum, described by Claparede and 

 Lachmann, in 1858, from specimens obtained at 

 Christiansand, Bergen, and a few other places in 

 Norway. 



:■: 



Fig. 23. Sand-grains and Amphi- 

 dinium (photo -micrograph under 

 low-power magnification). 



Fig. 24. Part of Fig. 23 under 

 high-power magnification. 



" The published records of Amphidinium, however, 

 do not give the impression that it is a common or 

 abundant organism. The latest comprehensive work on 

 such forms — the article on Peridiniales, by Paulsen, in 

 the ' Nordisches Plankton ' (Kiel, 1908)— recognises four 

 species of Amphidinium: A. crassum, A. rotundatum, 

 and A. longum, which as yet have been recorded from 

 Kiel only; and A. operculatum, which is stated to occur 

 in brackish water on the north coasts of Europe. In 



