PLATE X. 
Fig. 
18. Streptorhynchus pelargonatus, Schlotheim. ‘Testiferous specimen (large valve), 
twice the natural size. Dalton-le-Dale. 
19. = — Another specimen, differmg in form. Dalton-le-Dale. 
20. — = Another variety. Dalton-le-Dale. 
21. — os Lateral view (twice the natural size) of a cast. Dalton-le- 
Dale. 
22. — —~ Cardinal view of the last, showing the area and deltidium. 
a i a Testiferous specimens, twice the natural size, looking on 
9 5 me ae the small valve and area (a). Dalton-le-Dale. 
26. — — Cardinal view (twice the natural size) of other specimens : 
27. — _ } a, the deltidium or closed fissure. Dalton-le-Dale. 
28. aot = Enlarged view of the posterior half of the shell, showmg 
the dental plates (z) and socket-plates (4). Tunstall 
Hill. 
29. Productus horridus, J. de C. Sowerby. Front view (natural size) of the large valve 
of a testiferous specimen. Garmundsway. 
30. — — Umbonal view of the last specimen. 
31. — — Lateral view of the same. 
aS ee 
