PLATE I. 



(Permian Species.) 

 Fig. 

 1. Terebratula punctata, SowerbyA These specimens were figured in this place by mistake; they 

 2 — 4. Rhynchonella tetraedra, Sow. J belong to the Liassic period. 



5. Terebratula elongata, Schlotheim. A large specimen. Humbleton hill. Collection of Mr. 



Kirkby. 



6, 7- — — Two average-sized specimens. Tunstall hill. 

 8 — 11. — — var. sufflata. Different ages. Tunstall hill. 



12 — 14. — — Young specimen. Tunstall hill. 



15 — 17. — — var. sufflata. Casts. Humbleton. The letter N indicates the slit in 



the beak, due to the rostral plates. 



18. — — A remarkable internal cast from Humbleton, formerly in the collection of 



Mr. Howse, now in that of the Museum of Practical Geology. The 

 letter o refers to the curious impression explained in fig. 20. 



19. — — A very fine interior, showing the rostral plates of the dorsal valve, and 



loop in the ventral one : enlarged from a specimen in the collection of 

 Mr. Kirkby. 



20. — — A beautiful fragment, considerably enlarged, from Humbleton. In the 



collection of Mr. Howse. 



21. 22. — — Two interiors of the dorsal valve, to show small dissimilarities in the 



shape of the loop. 



23. Spirifera alata, Schlotheim. Internal cast of a large example. Humbleton hill. 



24. — — A trigonal specimen from Humbleton hill. Collection of Mr. Kirkby. 



25. — — A testiferous specimen. Tunstall hill. Collection of Mr. Kirkby. 



26. 27. — — Two specimens from Humbleton, showing the spirals. Collection of 



Mr. Kirkby. 

 28 — 31. — — Different specimens and ages from Humbleton and Tunstall hills. In 



the collection of Mr. Kirkby. 



32. — — Portion of the internal cast of the dorsal valve (enlarged), to show the 



position of the adductor impressions, aa; also of the cardinal process. 

 Collection of Mr. Howse. 



33. — — A gutta-percha impression from specimen, fig. 32 (less enlarged), show- 



ing the interior of the valve itself. 

 35,36. — — var. Permiana, King? Humbleton hill. 



37. Spiriferina cristata, Schlotheim. Tunstall hill. Collection of Mr. Kirkby. 



38, 39. — — Internal casts. Humbleton hill, n, slits left by the dental plates. 



40. — — Interior (magnified), showing the spirals in situ, from a perfect 



specimen. Humbleton. Collection of Mr. Kirkby. 



41. — multiplicata, Sowerby. (Enlarged.) Tunstall hill. 



42. — — Interior of the ventral valve (enlarged), to show the position of the 



central septum and dental plates. Collection of Mr. Kirkby. 



43. — — From Tunstall hill. 



44. — — A remarkable example, with unusually developed area, from Tunstall 



hill. Museum of Practical Geology. 

 45,46. ■ — cristata? Young shells. Tunstall hill. 



47 — 49. Spirifera Clannyana, King. (Enlarged.) Ry hope-field House. 



