EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Length 1 inch 4 hnes, width l^ inch. 



These casts have much the aspect of Mactraj ; the hinge is unknown. 

 Fig. S. Nucula oequalis. Transversely elongated, convex, marked with concentric 

 ridges ; anterior side rounded ; posterior separated by a ridge and truncated ; 

 beaks nearest the anterior side. 



Width twice the length, which is a quarter of an inch ; oa. is .3 h. magnified twice. 

 Fig. 4. Nucula accipiens. Transversely oval, convex, concentrically striated ; beaks 

 nearest the anterior side. 



Length 3^ lines, width above 4 lines. 

 Fig. 5. Nucula acuta. Transversely ovate, convex, concentrically striated, anterior 

 extremity rounded, posterior extremity produced, pointed. 

 Length 1 1 line, width 2^ lines ; 5a.\s.5h. magnified twice. 

 An elegant small shell. 

 Fig. 6. Unio Urii, (Fleming's British Animals, 417. Ures History of Rutherglen and 

 Kilbride, 311. t. 16. f. 4.). Transversely much elongated, very convex, wavy; 

 posterior extremity rather pointed ; beaks near the small anterior side. 



The general form approaches to cylindrical. Width 2i times the length, which 

 is about \\ inch. 



Fleming has confounded this with Unio oralis of Martin {Petri/. Derb. t. xxvii. 

 f, 1, 2.) which is quite distinct. 

 Fig. 7. Unio Ansticei. Very convex, wavy, curved, anterior side longest, forming a 

 lobe ; posterior side obtuse, gaping ? Surface concave towards the front ; beaks 

 near the anterior extremity. 7 a. Reduced figure to show the front of the shell. 

 Length 1^ inch, width 2| inches. 

 This has much the form of a Mya. 

 Fig. 8. Unio parallelus. Transversely elongated, rather flattened, wavy; sides almost 

 equally rounded ; front and back straight, parallel ; beaks near the anterior ex- 

 tremity. 8 a. Shows the depth of the valves. 

 Length 1 inch 4 hnes, width 2\ inches. 

 Fig. 9. Unio dolabratus. Subquadrate, wider than long, rather flat with an obhque 

 convexity along the middle, even ; anterior side small, rounded ; the posterior side 

 flattened and truncated ; beaks near the anterior side. 

 Length 13 lines, width about If inch. 

 Fig. 10. Unio modiolaris. Transversely elongated, convex, even, with an oblique 

 obtuse keel along the middle ; anterior side small, rounded ; the posterior trun- 

 cated, flattened ; beaks near the anterior side. 

 Length | inch, width about twice as much. 

 Fig. 11. Utiio Phaseolus. Transversely much elongated, three times as wide as long, 

 even, convex ; anterior side very small, pointed ; the posterior flattened, rounded. 

 Length 3 lines, width 7 lines. 

 Fig. 12. Unio aquilinus. Transversely ovate, curved, flattened, rugged; posterior 

 side pointed ; beaks near the rounded anterior side. 

 Length half the width, which is 14 lines. 



