62 BRITISH CRETACEOUS BRACHIOPODA. 



which it indents, and is more or less separated from the umbo ; beak ridges well defined, 

 leaving between them and the hinge margin a flat, false area ; the marginal line nearly 

 straight all round ; valves nearly equally convex ; surface ornamented by a variable number 

 of plaits, either simple or bifurcated, at irregular distances from the beaks and umbo. 

 Structure punctuated ; length 1 2, width 9, depth 7 lines. 



Obs. When young, the shells of this species present less convexity than at a more 

 advanced age, they are also very variable in the form and number of their plaits; in some 

 specimens, and more especially in the young, the costa) are all simple from the beak and 

 umbo to the margin, one or two only bifurcating on the sides ; but in the generality of 

 specimens, the bifurcation and intercalation of plaits at various distances from the beak 

 and umbo is very remarkable, particularly in some French shells, these bifurcate several 

 times before reaching the margin, presenting longitudinal undulations ; the number 

 therefore of the plaits is very variable ; we have specimens with from twenty to thirty 

 on each valve ; others with from thirty to forty-six ; sixteen to eighteen of which are due 

 to bifurcation and intercalation within the anterior third of the length of the valves. 

 This species is quite distinct from Ter. cardium, Lamarck ; although mistaken by some 

 authors, as Professor Bronn, 1 who believed it a simple synonym of the Lamarckian type. 

 T. oblonga is a much more oblong and oval shell ; the beak is more produced ; the 

 foramen completely different, being widely separated from the umbo, while in T. cardium 

 it lies almost contiguous to it, and the plaits are fewer in number, generally only bifurcating 

 in the young, while in the Cretaceous species this character is prevalent in all ages, and 

 especially in the advanced state ; I do not agree, therefore, with Mr. Austen, 2 when he 

 states that this species is common both to the Oolitic and Cretaceous Formations ; at least 

 after a minute examination of a multitude of Foreign and British specimens of both, I 

 have not come to that conclusion. 



I am not quite certain as to the genus to which this species belongs, from not 

 having been able to see the interior. M. D'Orbigny places it in his Terebratella, to which 

 it may, perhaps, belong ; but as he does not state it to have a doubly attached loop, I will 

 leave it for the present among the Terebratula. T. quadrata, Sow., is only an exceptional 

 variety of this species. T. oblonga is found in England, in the Lower Green Sand of 

 Atherfield, Hythe, near Devizes, Maidstone, and Farringdon, whence it has been collected 

 by Messrs. Walton, Harris, Morris, myself, and others ; it has likewise been found in the 

 Upper Green Sand of the neighbourhood of Warminster, by Mr. Cunnington, but the 

 species is very rare in that locality. In France, it occurs at Wassy, St. Dizier, &c, and is 

 well described and figured by M. D'Orbigny, in his 'Pal. Francaise;' in Switzerland, it is 

 mentioned from Neufchatel, and from several German localities, such as in the neighbour- 

 hood of Brunswick in the Hilsconglomerat of Essen, Schandelahe, Schoppenstedt, &c. 



1 Index Pal., p. 1243. 



2 'On the Lower Green Sand of Farringdon, &c.,' Quart. Journal of the Geol. Society, vol. iv, p, 477, 

 1850. 



