98 BRITISH CRETACEOUS BRACHIOPODA. 



46. Rhynchonella Gibbsiana, Sow. Sp. Plate XII, figs. 11, 12. 



Terebratula Gibbsiana, Sowerby. Min. Con., vol. vi, p. 72, tab. 537, fig. 4, 1829. 



— Gibbsii, Woodivard. A Synoptical Table of British Organic Remains, 



p. 21, 1830. 



— Gibbsiana, Morris. Catalogue, 1843. 



Diagnosis. Shell somewhat obtusely triangular, generally wider than long, with a 

 moderately developed mesial fold in the dorsal valve, to which corresponds a sinus in the 

 ventral one; beak acute, not much produced or incurved; foramen rather small, and 

 surrounded by a deltidium ; beak ridges sharply defined, with a flattened space between 

 them and the hinge line, margins sinuous, the frontal edge of the ventral valve greatly 

 indenting that of the opposite one. Each valve is exteriorly ornamented by from 45 to 

 50 small delicate plaits, 10 or 12 of these occupying the mesial fold and sinus. Dimensions 

 variable, the greatest depth near the umbo ; length 7^, width 9, depth 5 lines ; 



8 R 4-1 



Obs. M. d'Orbigny considers this shell to be a variety of B. sulcata, but I do 

 not feel prepared to admit that conclusion ; B. Gibbsiana appears to me to be a much 

 more triangular shell, with a deeper sinus, and externally ornamented by smaller or 

 more delicate plaits ; it seems peculiar to the Lower Green Sand, of Sandgate, Hythe, 

 Pluckley, Peasmarsh, as well as at Sandown and Atherfield, Isle of Wight, (collection of 

 Mr. S. Saxby). Some exceptional specimens found at Hythe bear resemblance to 

 B. latissima, Sow. 



The author of the ' Pal. Francaise,' moreover states, that the reference to this species 

 published by Professor Forbes in his ' Catalogue of the Lower Green Sand Fossils ' is 

 incorrect ; but on what grounds this assertion is made, I am at a loss to understand ; it 

 would, on the contrary, appear to me, that the French author had himself erroneously 

 identified our British type, which he refers to his Terrain Albian, which is not the age 

 of our fossil in the vicinity of Folkstone, or other British localities. 



Professor Bronn seems to be still further from the mark, while stating, in his ' Index 

 Palseontologicus/ that B. Gibbsiana is nothing more than a variety or synonyme of 

 B. plicatilis, Sow. ! 



Plate XII, fig. 11 . A specimen from the Lower Green Sand of Sandown, Isle of Wight. 

 „ fig. 12. A rather enlarged example, from the Lower Green Sand, at 



Pluckley, in the collection of Mr. Harris. 

 „ fig. 12 c Another specimen, nat. size, from Hythe. 



47. Rhynchonella lineolata, Phillips, Sp. Plate XII, figs. 6 — 10. 



Terebratula lineolata, Phillips. Geol. of Yorksli., vol. i, p. 178, pi. ii, fig. 27, 1835. 



— lineolata, Morris. Catalogue, 1843. 



