PLATE I. 



Fig. 

 1, 2°. 

 2*. 

 3. 



4, 5, 6. 



7. 



8. 



8\ 



8\ 



8'. 



S d . 



9. 



10,11. 

 12. 



is, n ab . 



14. 



15. 



16. 

 17. 



18. 

 19. 

 20 to 20. 



27. 

 28. 

 31. 



29, 30. 

 29". 



CRETACEOUS SPECIES. 



Crania Parisiensis. Interior of attached valve, enlarged. 

 „ „ „ of upper valve „ 



„ „ A portion of the Interior of attached valve, much 



enlarged. 

 „ ,, Exterior of both valves. 



„ „ A group of Cranias (from Meudon). 



Crania Egnabergensis, natural size : exterior of upper valve. 

 „ ,, Interior of attached valve, enlarged. 



„ „ Interior of upper valve „ 



„ ,, Exterior of attached valve : this specimen was only 



fixed by a small portion of the vertex ; enlarged. 

 „ „ A profile view of both valves, united and attached to 



a slender coral. 

 ,, ,, Exterior of attached valve, enlarged, showing the coral 



to which it was fixed. 

 ,, ,, Young specimens, with few costae. 



,, „ (Crania ovalis of Woodward), a malformation. 



,, ,, A specimen, fixed by a considerable portion of its 



lower valve to a shell. 

 ,, ,, Shows the valve not fixed by the whole surface, as in 



C. Parisiensis, figs. 5, 6, 7. 

 Thecidea Wetherellii, nat. size, fixed by nearly all the surface of the attached 



valve to an echinus. 

 Interior of the smaller valve, enlarged. 



„ larger valve ,, 



Exterior, enlarged illustration. 

 Profile view, enlarged. 



From the Chalk of Pewsey (Wilts). These different 

 enlarged illustrations show the variable manner in 

 which this species was fixed. 

 Lingula truncata, nat. size. 

 „ ,, Profile view. 



„ „ As figured by Dr. Fitton, from Hythe. 



,, subovalis, nat. size. 

 ,, ,, Interior enlarged. 



