loo Evolution and Distribution of Fishes 



upper bone bed. W. S. Symonds again {57: 186) writes: 

 "Near Kington the bone-bed of the Upper Ludlow rock is 

 there over-laid by brown-colored strata containing a typical 

 Upper Ludlow shell, Chonetes lata. These beds are again 

 overlaid by strata containing the remains of fishes, especial- 

 ly the Cyathaspis Banksii and portions of the crustacean 

 Pterygotus and also two species of Eurypteri." So we 

 would again reiterate that such remains of Lingula may 

 quite well have been derived as washouts and redeposits 

 from older rocks, or may have been washed up from a 

 marine habitat during high seas and mixed with remains 

 of the fishes in coastal lacustrine marshes. Further light 

 is shed on this later. 



As to the areal extent of this Upper Silurian Fauna 

 Woodward says: — "Its beginning is curiously marked over 

 an area of at least a thousand square miles by the Ludlow 

 Bone Bed, which is a layer of small and even minute fish- 

 fragments mingled with comminuted remains of other 

 animals which have been washed together. Notwithstand- 

 ing its great extent, this bone bed is rarely more than three 

 or four inches in thickness." Comparison with similar 

 beds of other lands strongly suggests that it may have been 

 many thousands of square miles in extent, and this is in line 

 with Woodward's suggestion of a possible correlation of 

 these beds with similar ones in Scotland and in the Baltic 

 area, a subject that is treated below. 



A paper on "The Highest Silurian Rocks of the Ludlow 

 District" {38: 195) by Misses Elles and Slater is specially 

 detailed and suggestive. They say: — "In the Ludlow- 

 Downton district there exists an interesting series of rocks, 

 limited by the Aymestry Limestone at their base and the 

 Old Red Sandstone at their summit, and it is with these 

 that the present paper deals. Lithologically they present 

 a varied series of sediments ranging from limestones on 

 the one hand, through calcareous flagstones and shales to 

 shallow-water sandstones on the other; and these litho- 

 logical changes are associated with certain changes in the 

 fauna. 



"Palaeontologically, these rocks are characterized by the 

 presence of Eurypteridae, which, although rare in the lower 



