OF CONCHOLOGY. 119 



across the \v horls ; a carinated ridge 

 round the margin at the base ; aper- 

 ture angulated, and slanting towards 

 the base. 



Linn. Trans, vol. viii. page 188. 



Not uncommon in ponds, rivers, 

 and ditches : they are of a very large 

 size at P rest wick-water, near New- 

 castle on Tyne. 



PLATE IV. 



HINGES OF BIVALVES, <&C 



Fig 1st. Hinge of the My a Pic- 

 torum. a Primary tooth, cc double 

 teeth. 



Fig. 2nd. Hinge of the Solen Sili- 

 qua. b Lateral teeth. 



Fig. 3d. Hinge of the Tellina 

 Radula. a a Primary teeth, n carti- 

 lage. 



