72 BRITISH CRETACEOUS BRACHIOPODA. 



30. Terebratula Carteri, Dav. PL VII, fig. 3. 



Diagnosis. Shell elongated oval, or unequally five sided, and somewhat compressed ; 

 ventral valve deeper than the dorsal one, with a shallow longitudinal sinus corresponding 

 with a mesial fold of moderate elevation ; beak short, slightly incurved, and truncated by 

 a foramen of moderate dimensions ; deltidium almost inconspicuous. Surface smooth, 

 marked by a few concentric lines of growth. Lateral margins slightly flexuous, with the 

 ventral frontal edge indenting that of the dorsal valve. Loop unknown, but in all pro- 

 bability short and simple. Length 20, width 15, depth 10 lines. 



05s. I obtained this shell some years ago from the Gray Chalk, near Dover, and have 

 been unable to identify it with any of the other British Cretaceous forms that have come 

 under my observation, it bears much of the outward aspect of some Jurassic Terebratula?, 

 although perfectly identical with none of those with which I have compared it. I there- 

 fore take great pleasure in naming it after Mr. Carter, who has afforded such valuable 

 assistance in the working out of the Cambridge Upper Green Sand species. 



Plate VII, fig. 3. Ter. Carteri, from the Gray Chalk in the vicinity of Dover. 



31. Terebratula Robertoni, If Arcldac. Plate IX, fig. 25. 



Terebratula Robertoni, D' 'Archiac, Mem. Soc. Geol. de France, vol. ii, 2d series, 



p. 315, pi. xviii, fig. 2, 1847. 

 — — Sharpe, Quart. Journ. of the Geol. Soc., vol. x, p. 192, 



1853. 



Diagnosis. Shell of an elongated oval shape ; valves regularly convex, the ventral one 

 rather the deepest ; surface smooth, marked by concentric lines of growth ; beak mode- 

 rately produced, incurved and truncated by a large circular foramen, partly margined by a 

 short deltidium ; ventral valve somewhat keeled ; beak ridges undefined, lateral margins 

 flexuous , the frontal edge of the ventral valve slightly indenting the opposite one. Loop 

 unknown, probably short and simple. Length 11, width 8, depth 5^ lines. 



Obs. Viscount D'Archiac states 1 that Ter. Robertoni differs from T. depressa, Lamarck 

 (his T. nerviensis), by its more regularly rhomboidal form, unequal depth of the valves, 

 almost entire absence of sinuosity in front, and above all by the inflated extremity of its 

 prominent and incurved beak. M. D'Orbigny appears to consider T. Robertoni as a 

 simple synonyme of T. biplicata / but this appears far from being the case, since it does 

 not present any trace of biplication, a character always more or less visible in Brocchi's 

 species, and it differs likewise in external shape. T. Robertoni wasf ound in the Sponge 

 Gravel of the Upper Green Sand of Farringdon, by Mr. Lowe, it agrees exactly both in 



1 'Rapport sur les Fossiles du Tourtia, p. 315. 



2 'Prodrome,' vol. ii, p. 1/2. 



