CO'i^CB.YLlA—DITHYRA. 53. 241 



Turton, British Fauna, p. 165. 



Ldnn. Trans, viii. tab. 3, A. fig. 3. 



Dorset. Catal. p. 40, tab. 13, fig. 6. 



Dillwyn, Descript. Catal. p. 317. 



Turton, Conch. Diet. p. 116. 

 Musculus tenuis. Lister, Conch, tab. 153, fig. 8. 

 Mus. nost. In ponds and deep rivers. 



Shell about half the size of the last, covered with a brown or 

 blackish skin which forms a membrane beyond the margin ; the an- 

 terior side winged, angular, and somewhat truncate ; the margin 

 opposite the hinge running nearly straight, or slightly indented : the 

 space about the hinge always much decorticated as if worm-eaten, 

 like the Unio margaritiferus. 



Anodon testa oblongd depressiusculd, lateribus rotundatis, margine Avonensis. 



rectiusculo, umbonibus subterminalibus. 

 Shell oblong flattish, rounded at both the sides, with the margin 



nearly straight, and the beaks almost terminal. 

 Mytilus Avonensis. Montagu, Test. Brit. p. 172. 

 Turton, British Fauna, p. 165. 

 Linn. Trans, viii. p. 110, tab. 3, A. fig. 4. 

 Turton, Conch. Diet. p. 116. 

 Mus. nost. From the Avon, in Wiltshire and Oxfordshire. 



Shell rather less than the last, of an olive brown color, with the 

 front margin nearly straight or slightly arcuated towards the smaller 

 end, and the hinge near one end. 



2; 



