338 Dr. FiTTON on the Strata below the Chalk. [App. A. 



Fig. 3. Trigonia spinosa, var. Distinguished from Trigonia spinosa (Min. Conch, t. Ixxxvi.), 

 of which it is a variety, by tlie presence of longitudinal ridges continued from the bases of the 

 spines, and by its more oblique form. It is often longer than the specimen here figured. 



Fig. 4. Diceras Lonsdalii. The small portion hitherto examined of the external impression 

 of this curious fossil, shows the shell to have been squaraose, like an Oyster, and of considerable 

 thickness. The two valves are less equal in size than is usual in the genus Diceras. The 

 larger valve is an elongated cone, rather flattened and curved twice round; and it appears to have 

 been attached to some foreign body, as in Diceras arictinum. The other valve has only an 

 oblique conical umbo. 



PLATE XIV. 



Fig. 1. Pliolas giganteus. In general aspect much resembles a Pholadomya ; but the appa- 

 rently squamose structure of the surface shows it to belong to the same section of the Pholades as 

 P. Candidas. Its valves are so convex as to form nearly a cylinder when closed. The reflected 

 margin near the beak, so large in some Pholades, is probably broken away in this specimen. 



Fig. 2. Modiola lineata. The depth of each valve is equal to its width ; the beaks are ob- 

 tuse ; the margins are arched and nearly parallel ; the surface longitudinally and finely striated. 



Fig. 3. Avicula pectinata. A slightly convex shell, with large, square, depressed ears, and 

 short acute linear ridges, alternately longer. 



Fig. 4. Ostrea relusa. This, like most Oysters, is very variable in form, but generally much 

 curved and nearly orbicular ; the shell is moderately thick, plain in the middle, but strongly 

 plicated at the margin with angular plaits. It occurs in massy groups. It is not so flat as 

 O. semiplana, a fossil of the chalk ; nor are its valves so equal, nor so thin, as in that species, 

 which it otherwise much resembles. 



Fig. 5. Anomia rad'iata. Irregularly orbicular, flat, finely radiated. The radii are coarser, 

 and more distant, than the fine striaj which occur in the London clay species, Anomia lineata, 

 (Min. Conch, t. 425.) 



Fig. 6. Anomia Icevigata. Much smoother, and more even, than any other known species : 

 very thin, orbicular, and flat. The figures a. and b. are taken from different specimens ; a. in 

 Mr. Smith's collections ; b. in Mr. Sowerby's. 



Fig. 7. Anomia convexa. A remarkably convex species, wiih a large and prominent beak, 

 and smooth surface. The furrows are produced by a Terebratula to which this specimen was 

 attached, and to which it consequently bears a great resemblance. 



[The name of this new species has been omitted, by mistake, in the list of Lower green-sand 

 fossils of the Isle of Wight, p. 204. It was found there in the debris fallen from the cliff, on the 

 shore east of Shanklin Chine.] 



Fig. 8. Terebratula Tamarindus. Nearly orbicular, smooth ; margin very obtuse. Disk 

 rather flattened ; beaks but little curved, with an angular, slightly prominent ridge on each side, 

 passing down the sides of the valves. 



Fig. 9. Terebratula quadrata. Ovate, gibbose ; beuk large ; front broad, straight, with a 

 few large plaits. 



Fig. 10. Terebratula Faba. Elliptical, narrow, gibbose; front concave, but not elevated, 

 very narrow ; the perforated beak short, but prominent. 



Fig. 11. Terebratula elegans. Transversely obovate ; beak prominent, pointed, nearly straight ; 

 plaits numerous, sharp ; front slightly elevated, straight. 



Fig. 12. Terebratula convexa. Angles rounded; valves very regularly convex ; beak large; 

 plaits numerous, rounded ; front slightly elevated. 



