96 BRITISH CRETACEOUS BRACHIOPODA. 



Plate XII, fig. 15. A typical example (fig. 15 a, b, enlarged) from the Grey Chalk 



in the vicinity of Eolkstone, I avail myself of this occasion 

 to thank Mr. Mackie for the opportunity he has kindly afforded 

 me in the examination of an extensive series of this and other 

 species from his locality. 



„ fig. 16. A specimen from the Chalk Detritus of Charing (Kent), in the 

 collection of Mr. Harris : — fig. I6 a is an enlarged illustration, to 

 show how the plaits augment at times by intercalation ; this is, 

 however, an extreme case, as in the generality of specimens 

 the plaits appear more regular. 



„ fig. 16^. A specimen from the Upper Green Sand of Chute, near Warmin- 

 ster; from the cabinet of Mr. Cunnington. 



44. Rhynchonella Grasiana, D'Orbigny. Plate XII, figs. 17, 19. 



Rhynchonella Gbasiana, IfOrbigny. Pal. Fran?., Ter. Cretaces, vol. iv, p. 497, 



figs. 7—11, 1847. 



Diagnosis. — Shell transversely oval, somewhat obtusely five-sided; slightly indented 

 in front. Valves unequally convex, the dorsal or socket one commonly the deepest, with- 

 out a produced prominent mesial fold. In the ventral valve a wide longitudinal sinus of 

 moderate depth, extends from near the centre of the valve to the front, where the 

 margin indents considerably that of the opposite valve ; beak short, acute ; foramen small, 

 and entirely surrounded by the large tubular expansions of the deltidium ; a flattened 

 space exists between the beak ridges and hinge line, which last slightly indents the 

 lateral margins of the umbo. Externally each valve is ornamented by from 46 to 56 

 small plaits, at times augmented by the intercalation of smaller ones at various distances 

 from the beak and umbo. Length 5, width 5, depth 3 lines. 



Obs. We need not repeat the observations relative to this form noticed under 

 B. Martini (Mantel!) ; but it would appear that some French examples have attained 

 larger dimensions than any hitherto obtained from our British localities ; thus a well 

 formed specimen from the Basse Alpes (for which I am indebted to M. d'Orbigny), mea- 

 sures, length 7, width 7, depth 5 lines; and I have seen a few even exceeding those 

 measurements. The author of the ' Pal. Franc' justly observes, that certain examples of 

 this species somewhat resemble B. Cuvieri (D'Orb.) in their external contour, but may be 

 distinguished by the greater number of plaits, position of the foramen, and less sinuous 

 margins. 



B. Grasiana abounds in the Upper Green Sand of Chute, near Warminster, in 

 Ferruginous Beds of the same age near Clifton Hampden (Mr. Sharpe's collection), and 

 in the Chloritic beds of Chardstock. In France, it is found in the Upper Green Sand 

 near Havre (Seine Inf.), and in the neighbourhood of Grasse. 



