PLATE XVII. 



Fig. 

 1,2, 



4, 4 ". 



5. 



G to 12 



13. 



14. 

 15. 



]5" ic 



16. 



17. 



~l r/a b c 



18. 



19. 



3. Rhynchonella obsoleta. Different ages; fig. 1 is the largest example I have 



seen in England. 

 ,, Interior, a, the two short curved lamella to which 



the arms were affixed ; b, muscular impressions. 

 ,, Beak, showing the foramen entirely surrounded by the 



deltidium and separated from the umbo, which 

 character distinguishes this species from R. concinna. 

 concinna. Different stages of growth and varieties; figs. 9, 10. 

 T. flabellula, of Sow., fig. 12, illustrates the beak, 

 deltidium, and foramen, 

 angnlata. Drawn from Mr. Sowerby's original specimen and type, 

 sub-obsoleta. The largest specimen I have seen, 

 varians, nat. size. 

 „ enlarged. 



Profile of another specimen, 

 sub-concinna, nat. size. 

 ,, Enlarged figure. 



? An undetermined form : it looks like a small R. tetraedra, 

 but is from the Upper Calcareous Grits of Scar- 

 borough, in the collection of Mr. Bean : having only 

 seen one example, I have not ventured to give it a 

 name, and place it here, from its being the only 

 form I have observed from this bed. 

 Forbesei, nat. size. 



„ enlarged figures. 



