268 JOURNAL OF CONCHOLOGY. 



FRESH WATER MUSSELS IN THE OUSE AND FOSS. 



By the Rev. W. C. HEY, M.A. 



Read before the Yorkshire Philosophical Society. 



The Ouse and the Foss, which unite just below York at the 

 spot known as the Blue Bridge, are rivers of very different 

 character, much more so than the superficial observer would 

 suppose. The Ouse is a wide, deep, and generally rather a rapid 

 river, sometimes, in floods, almost a torrent. The Foss is a 

 narrow river, naturally shallow, though in parts deepened artifi- 

 cially, and the current floAvs so gently that often the water is 

 practically stagnant. Again, the Ouse has a very bare channel 

 somewhat hard and stony in places, and even where the bottom 

 is soft and sandy there is no vegetable growth. But the Foss has 

 a bottom of rich soft mud, where the flags and the water-lilies 

 root themselves and flourish luxuriantly. In places the river is 

 quite overgrown with tall rushes in summer time. Again, the 

 Ouse receives a good deal of drainage, the Foss not much, except 

 one very poisonous kind, viz., that which escapes the Gas Works. 

 Once more, near York the Ouse has no locks. This is a very 

 important point to notice in regard to the distribution of species. 

 But the Foss has three locks within the space of as many miles, 

 viz.. Castle Mills Lock, Yearsley Lock, and Huntington Lock. 

 Asking you to bear in mind these points of contrast between the 

 Ouse and the Foss, I go on to make a few remarks on the genera 

 and species of mussels found in these rivers. The family of 

 UnioTiidcE or freshwater mussels is represented in England by two 

 genera, viz., Unio and Anodonta. This is the distinction between 

 them. In Unio the hinge, or point upon which the valves work, 

 is supplied with projections known as teeth, and corresponding 

 receptacles. In Anodonta the hinge-line is quite smooth and 



J.C, iii., January, 1882 



