In Silurian and Devonian Epochs 123 



characters, nor does their being associated with some 

 thousand feet of sandstones and conglomerates render it 

 impossible that they themselves should have been formed 

 in freshwater or brakish water." But his subsequent re- 

 marks indicate that his mind was in a somewhat uncertain 

 state. 



On page 16 he makes the very significant observation 

 that the Estheria tests "are found in a thin bed, and lie 

 in great quantities on the surface planes, never to any 

 depth, but just as it were interleaved. Here, as well as 

 at all the other localities, they are accompanied by scales 

 of fishes and pieces of bone." Now, from direct observa- 

 tion by the writer on the deposits of mud and sand over the 

 wide flood-plains of Southern States rivers, from our 

 knowledge of the greatly more extended periodic river- 

 floods of the Orinoco, Congo, and other continental rivers, 

 the above observation suggests that each "thin bed" of 

 Old Red rock, represented a periodic flood deposit, and on 

 retreat of the waters shallow marshy areas were left in 

 which, as with present-day Estherieae, the tiny organisms 

 multiplied prodigiously. When the next succeeding per- 

 iodic inundation took place, fish scales and bones, plant 

 remains and other organic debris would be deposited, suc- 

 ceeded by a new "thin bed" of mud or fine sand that sealed 

 up the Estherieae "in great quantities on the surface 

 planes." This is in line also with Barrell's contention (79 : 



33S)- 



Here it may appropriately be added that Jones ob- 

 tained specimens of Estheria inembranacea from Livonia 

 in Russia, and says (p. 18) "these are identical with the 

 Estheriae from Caithness." Also (p. 20) "on the river 

 Torgel in Livland Dr. Pander found that the hard white 

 sandstones used for grindstones, contain fine remains of 

 Asterolepis (Pander) and that the overlying bluish marls 

 and clays contain scales and teeth of Osteolepis, Dipterus 

 and Glyptolepis in company with Estheria membranacea." 



The fish fauna of the Upper Old Red rocks is a varied 

 but steadily evolving one. In addition to clumsy heavily- 



