TEREBRATULA. 59 



surrounded by, and widely separated from the hinge line by a deltidium in two pieces ; 

 beak ridges undefined, lateral margins flexuous, slightly raised and bisinuated in front. 

 The dorsal or socket valve is biplicated towards the front; surface smooth, with a few con- 

 centric lines of growth. Loop short, not exceeding a third of the length of the dorsal 

 valve; shell structure minutely punctated. Dimensions variable; length 18, width 12, 

 depth 9^ lines. 



Obs. This species appears to be readily distinguished from Ter. biplicata by its very 

 elongated oval shape ; the cardinal half becoming considerably lengthened, gives the shell 

 a somewhat scuttle-shaped appearance : while, on the contrary, T biplicata is more pen- 

 tagonal and rounded near the beak ; the last becoming incurved, with the foramen 

 situated so close to the hinge line, as to render the deltidium almost inconspicuous. 

 Some exceptional examples might perhaps be obtained connecting the two forms, but 

 these not having yet been procured, we must continue to consider this species as distinct. 



Ter. prcdonga appears to characterise the Lower Green Sand {Neocomien of the French), 

 while the Ter. biplicata chiefly occurs in the Gault and Upper Green Sand. 



T. prcelonga was well figured by Sowerby in 1836 from a specimen stated to have 

 been found in the Lower Green Sand of Sandgate (Kent) ; it occurs likewise near 

 Maidstone (Kent), and in other localities ; but it is one of our rarer British species. 



On the Continent, M. D'Orbigny mentions it from the Lower Neocomien beds of 

 Baudrecourt, Bettancourt-la-Eerree (Haute Marne), Morteau (Doubs), the neighbourhood 

 of Castellane and Marolles (Aube), at Neuchatel in Switzerland, &c. 



Plate VIT, fig. 1 . Type example from the Lower Green Sand of Sandgate, figured by 

 Sowerby in Trans. Geol. Soc. 

 „ fig. 2. A very fine specimen from a similar bed at Maidstone, in the Col- 



lection of Mr. Morris. 



24. Terebratula sella, Sowerby. Plate VII, figs. 4 — 10. 



Terebratula sella, Sowerby. Min. Con., vol. v, p. 53, pi. 437, fig. 1, 1825. 



— — Fleming. A Hist, of British Animals, vol. i, p. 371, 1828. 



— — Woodward. A Synoptical Table of Brit. Org. Remains, p. 21, 



1830, (marked Up. Oolite by mistake.) 



— biplicata (part), V. Buck. Classification des Terebratules, Mem. Soc. 



Geol. de France, vol. iii, p. 218, 1834. 



— sella, Brown. Must, of Fossil Conch, of Great Britain, pi. Iii, figs. 31, 



32, 1838. 



— — Roemer. Kreid., p. 43, No. 41, 1840. 



— biplicata, Roemer. lb., pi. vii, fig. 17, 1840. 



— sella, Leymerie. Mem. Soc. Geol. de France, vol. v, p. 30, 1842. 



— — Morris. Catalogue, 1843. 



— — Forbes. Quart. Journ. Geol. Soc, vol. i, p. 345, 1845. 



— biplicata, (part) Bronn. Index Pal., p. 1230, 1848. 



