94 BRITISH CRETACEOUS BRACHIOPODA. 



one character, as may be easily perceived by comparing the figures or examples of the two 

 species. 



B. nuciformis is not very rare in the Upper Green Sand of Farringdon ; it also occurs 

 in the Chloritic Beds of Chardstock, where it has been collected by Mr. Wiest, &c. 



Plate XI, figs. 23 and 24. Two typical examples from the Upper Green Sand of 



Farringdon (collection of Mr. Sharpe) ; fig. 23" h c , are 

 enlarged representations to show the character of the 

 plaits. 

 ,, fig. 25. A transverse and less globose specimen, from the same locality 



and collection. 

 ,, figs. 26 and 27. Two other examples from Farringdon, in the cabinet of 



Mr. Lowe. 

 Plate XII, fig. 27. From the Upper Green Sand of Niton, Isle of Wight, in the collec- 

 tion of Mr. S. H. Saxby. 



43. Rhynchonella Martini, Mantel!, Sp. Plate XII, figs. 15, 16. 



Terebratula Martini, Mantell. Geo!, of Sussex, p. 131, 1822. 



— pisum, Sowerby. Min. Con., vol. vi, p. 70, tab. 536, figs. 6, 7, 1826. 



— — Fleming. A Hist, of British Animals, vol. i, p. 374, 1828. 



— — Woodward. A Synop. Table of British Org. Remains, p. 21, 1830. 



— — V. Buck. Class, des Terebratules, Mem. de la Soc. Geol. de 



France, vol. iii, p. 148, pi. xv, fig. 18 bis, 1838. 



— brevirostris, Rcemer. Die Vers. Nord. Kreid., pi. vii, fig. 7, 1840. 



— Martini, Morris. Catalogue, 1843. 

 Rhynchonella pisum, D'Orb. Prodrome, vol. ii, p. 171, 1850. 



Diagnosis. Shell sub-orbicular, longer than wide, nearly square in front : valves 

 almost equally convex, with the greater.t depth at a short distance from the beaks, a slight 

 longitudinal depression existing towards the front of either valve : no regular sinus nor 

 mesial fold : margin nearly straight all round or slightly raised in front: beak short, acute, 

 and moderately incurved, with a flattened space between the beak ridges and hinge line : 

 foramen small, contiguous to the umbo, and entirely surrounded by a deltidium and its 

 tubular prolongations : externally each valve is ornamented by from 30 to 40 delicate 

 plaits, intersected by numerous concentric lines of growth. Length 4^, width 4, 

 depth 2^ lines. 



Obs. B. Martini is a small shell, never greatly exceeding the dimensions above stated, 

 and more often not as large. The plaits are narrow, delicate, and augment here and there 

 by intercalation : the numerous, closely packed, and slightly raised concentric lines of 

 growth gives to the ridges of the plaits a granulated aspect, which is more deceptive than 

 real. 



This species was, for the first time, named and described by the celebrated author of 



