Notes on the Collection of Fossil Fishes from the Upper Laas 
of Ilminster in the Bath Museum. By ARTHUR SMITH 
Woopwarp, F.G.S., of the British Museum. 
(Read January 15th, 1896). 
The distribution of fossil fishes in the stratified rocks is very 
remarkable, With rare exceptions, good specimens occur only in 
certain definite thin layers where they are discovered in great 
shoals. Fragments are also often curiously swept together to 
form a veritable ‘‘bone-bed,” perhaps not more than a few 
inches in thickness though extending over many square miles of 
country. Hundreds or thousands of feet of sediment certainly 
deposited in a sea well-tenanted with fishes, are not uncommonly 
destitute of all traces of their skeletons except an occasional 
tooth or scale; while a local layer in the midst of one of these 
series may unexpectedly reveal a rich and varied fauna. On 
examining specimens from such layers, it will often be observed 
that they exhibit a gaping mouth or some signs of contortion 
at death ; there are also geological reasons for supposing that 
they have been quickly covered up with sediment. The general 
conclusion is, therefore, that whole shoals of fishes have been 
suddenly destroyed at these spots, either by an escape of noxious 
gases into the sea, or by a cloud of mud in some current, or by 
another unfavourable change in their surroundings. The various 
samples of the fish-life of different periods have thus been pre- 
served by mere local accident ; the discovery of them by us 
depends again merely upon accident. Hence our knowledge of 
the fishes of past ages consists almost entirely of little discon- 
nected items culled from widely-separated zones scattered through 
the rocks of different parts of the world. 
The period of the Upper Lias happens to be represented by 
