88 BRITISH CRETACEOUS BRACHIOPODA. 



convex, with a shallow longitudinal depression or sinus in the dental or ventral valve, 

 which corresponds to a slightly produced mesial fold in the opposite one. Beak short, 

 entire, not much incurved, foramen small, and entirely surrounded by the deltidium : lateral 

 margins almost straight : the frontal edge of the ventral valve encroaches on that of the 

 dorsal one. Externally each valve is ornamented by from 15 to 18 wide simple plaits, 

 3 or 4 forming the mesial fold. Dimensions' very variable : length 7, width 8, depth 4^ lines. 

 05s. This species was accurately described and figured by Sowerby, in the ' Mineral 

 Conchology,' under the name of Ter. Mantelliana ; and it is most probably one of the shells 

 intended by Parkinson as the type of his Ter. sulcata, but as the last-named author neither 

 described nor figured his form, Sowerby's denomination must be retained for the well- 

 known species under consideration. 



Bh. Mantelliana is commonly a small shell, of about the dimensions above given, 

 but it has been found sometimes, although rarely, of larger dimensions, as proved by 

 the fine specimen (PI. XII, fig. 23) found in the Lower Chalk near Lewes, by Mantell, 

 and it forms part of his collection in the British Museum ; it abounds in the Lower Chalk 

 and Chalk Marl between Dover and Folkstone, at Hamsey, and in many other localities, 

 and has been collected, although much more rarely, in the Upper Green Sand of the 

 neighbourhood of Warminster, and in the Chloritic Marl of Bonchurch (Isle of Wight), 

 by Mr. S. H. Saxby. On the Continent, it occurs in beds of a similar age to those above 

 mentioned, both 'in France and Belgium. Bh. Mantelliana is well distinguished from 

 Bh. Cuvieri, by its larger and less numerous plaits, as well as by its greater width. 



Tlate XII, fig. 20 and 21. Two examples from the Gray Chalk of Folkstone and 



Hamsey. 

 ,, fig. 22. A specimen from the Upper Green Sand of Chute Farm, near 



Warminster, in the collection of Mr. Cunnington. 

 ,, fig. 23. A very large specimen, from the Lower Chalk of Lewes, in the 

 Mantelliaii collection in the British Museum. It measures : 

 length 10, width 11, depth 6^ lines. 



40. Rhynchonella Cuvieri, D ' Orbigny. Plate X, figs. 50 — 54. 



Terebratula pisum, Geinitz. Kreide, pi. xvi, fig. 18, 18-10 (but not Ter. pisum, 



Sow.). 

 Rhynchonella Cuvieri, B'Orbigny. Pal. Fran^., Ter. Cretaces, vol. iv, p. 39, pi. 497, 



figs. 12—15, 1847. 



Diagnosis. Shell small, transversely or longitudinally oval, length and width often 

 the same : valves regularly convex, and of nearly equal depth, a shallow depression or sinus 

 existing towards the front of the dental or ventral valve, to which a similar slight eleva- 

 tion corresponds in the opposite one ; beak small, acute, and entire ; foramen minute, com- 

 pletely surrounded and removed from the contiguity of the hinge line by a deltidium and 



