78 THE DISPERSAL OF SHELLS. 



the valves of a fresh-water mussel. His informant's 

 sons were fishing in a pond at Hole Park_, at Rolven- 

 den, Kent, and the water being low, they were able to 

 obtain a number of mussels, in one of which they found 

 a claw which was regarded by the Editor of the Fields 

 to whom it was submitted, as the *' hind toe of some 

 species of Ttirdusl' probably a blackbird. The 

 specimen is now preserved in the British Museum 

 (Natural History), Cromwell Road. It appeared that 

 the toe, the tendon of which protruded from the shell, 

 had been torn off by the bird in endeavouring to free 

 itself from the grasp of the mollusc. A larger bird, of 

 course, would have flown away with the shell. As 

 Godwin-Austen observes : — 



" The great interest that surrounds this well authen- 

 ticated observation is its connection with the distribution 

 of species. The very slight divergence in the characters 

 of the genus Unio and of Anodonta all over the world 

 is a very well-known fact. They are constant over 

 enormous areas, few groups are more so, and here we 

 find an admirable example of how they must, from 

 time to time, be carried from one piece of water, or 

 from one river system to another. A specimen full of 

 ova (which are particularly numerous), might in this 

 manner be conveyed many hundred miles in a single 

 night, when aquatic birds are on their migration, and 

 thus stock a new habitat." ^ 



A large fresh-water mussel [Anodonta), upon the foot 



' H. H .Godwin-Austen, F.R.S., " Bird captured by a Fresh-water 

 Mussel," "Field," Ixvi. (1885), 499. 



