UPPER, OR FLINTY CHALK. 217 



This species differs from I. Brongniarti, in the ridges being distant, and 

 irregular ; and from the young of I. Lamarckii, in the greatest convexity 

 being near the beaks, and not in the centre of the valves, as in that species. 

 It is a small shell, seldom exceeding the size of the figure, and is named 

 in commemoration of the interesting researches of Thomas Webster, Esq. 

 keeper of the Museum of the Geological Society, whose unassuming 

 manners, and extensive information, have obtained him the respect, and 

 esteem, of all who have the pleasure of his acquaintance. 



Locality. Lower chalk, South-street : very rare. 



89. Inoceramus striatus. Tab. xxvii. fig. 5. 



Gibbous, rounded, even, with numerous transverse striae ; hinge ob- 

 lique ? beaks ? 



The roundness of this shell, and its finely striated surface, readily distin- 

 guish it. The specimen figured, has a ridge down the convex part of 

 the valve ; but as this appearance is not constant, it is omitted in the 

 specific description. A perfect example has not been discovered. 



Locality. Lower chalk, South-street : very rare. It occurs also in 

 the chalk near Heytesbury, Wilts. 



90. Inoceramus undulatus. Tab. xxvii. fig. 6. 



Convex, marked with numerous, regular, transverse elevations, and de- 

 pressions ; posterior slope truncated ; hinge side expanded. 



The surface being gently undulated by the round, even, alternate 

 elevations, and depressions, this shell has a peculiarly neat appearance. 

 The posterior slope is flat, and nearly smooth. The valves are regularly 

 convex, but hoUowed or contracted on the anterior side, which is ex- 

 panded. The beaks are rounded, and incurved. 



LocaUty. Upper chalk, near Lewes. 



91. Inoceramus . Tab. xxvii, fig. 9. 



This shell is rather depressed near the beaks, and inflected in front ; 

 it has numerous concentric ridges and striae. It is in too mutilated a 

 state to admit of a more particular description. 



Locality. Lower chalk, Lewes. 



Fragments of other species of Inoceramus occur in the chalk in the 



F F 



