TEREBRATULA. 61 



Plate VII, fig. 6. From the Isle of Wight. 



fig. 7. From Gault near Maidstone ; in Mr. Bowerbank's museum. 

 ,, fig. 8. A specimen from the Isle of Wight, in the Geol. Society's Museum. 



„ fig. 9. From the same locality, in the Collection of Mr. Morris. 



„ fig. 10. A young shell; Isle of Wight. 



25. Terebratula TORNACENCis,Var. rcemeri, D'Archiac. Plate VII, figs. 11 — 16, and 

 Plate IX, figs. 1—8. 



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



p. 318, pi. xviii, figs. 2—5, 1847. 



— Rcemeri, D'Archiac. lb., pi. xviii, fig. 6. 



— Bouei, D'Archiac. lb., pi. xviii, fig. 7. 



— crassa, D'Archiac. lb., pi. xviii, fig. 8. 



— crassificata, D'Archiac. lb., pi. xix, fig. 1. 



— rustica, D'Archiac. lb., pi. xix, fig. 2. 



— biplicata, D' Orbigny ? (not Brocchi nor Sowerby), Pal. Franc., Terrains 



Cretaces, vol. iv, pi. 511, figs. 9—15, 1847. 



— Rcemeri, Sharpe. Quart. Journ. Geol. Soc, vol. x, p. 191, 1853. 



— Keyserlingii, Sharpe. lb. 



— revoluta, Sharpe. lb. ? 



Diagnosis. Shell variable in shape, somewhat pentagonal ; as long as or longer than 

 wide; valves almost equally convex or flattened. Dorsal valve more or less distinctly 

 biplicated towards the front. Ventral valve with a mesial plait corresponding with the sinus of 

 the opposite one. Beak produced, slightly incurved and truncated by a rather large circular 

 foramen, partly edged by a deltidium of moderate dimensions; beak ridges tolerably 

 defined, with a flattened space between them and the hinge line ; lateral margins some- 

 what fiexuous and bisinuated in front. External surface smooth, at times obscurely longi- 

 tudinally striated and marked by numerous concentric lines of growth ; shell structure 

 largely punctated. Loop short and simple, not exceeding a third of the length of the 

 smaller valve. Dimensions very variable : 



length 10, width 8^, depth 5 lines. 



„ 8, „ 8, „ 3 „ &c. 



Obs. The most common species in the Sponge Gravel or Upper Green Sand of 

 Farringdon is that represented in PI. VII, figs. 11 — 16, and PI. IX. figs. 1 — 8, of the present 

 Monograph ; it rarely exceeds 9 lines in length, with from 7 to 9 in breadth, is either 

 elongated and moderately convex (PL VII, figs. 12, 13, 15, and PI. IX, figs. 1, 2, 3, and 8), 

 or as wide as long, and more or less compressed (PI. VII, figs. 11, 13 a , 14, and PI. IX, 

 figs. 4 to 7). These shells present every kind of variation, but they are connected by 

 insensible passages, and unquestionably, in my opinion, belong to the same species. 



