214 UPPER, OR FLINTY CHALK. 



individual imbedded in a block of chalk : the hinge groove is placed be- 

 neath the obhque line on the left side of the uppermost valve. 



Locahties. Common in the Upper chalk, near Lewes, Eastbourne, 

 &c. 



84. Inoceramus Lamarckii. Tab. xxvii. fig. 1. 



Valves equal, very convex, with a few obscure, longitudinal undula- 

 tions, and distant transverse ridges ; surface covered with numerous con- 

 centric striae ; posterior slope subdepressed ; anterior side lobate, expanded; 

 hinge nearly transverse. 



Both valves are equally convex, and gradually expand towards the 

 'margin ; the greatest convexity being near the middle of the shell, which 

 is suddenly contracted longitudinally, and has a lobated appearance on 

 the hinge side. The beaks are incurved and inclined toward the pos- 

 terior slope, which is shghtly concave. The anterior side is convex, ex- 

 panded, and separated from the body of the valve by a deep furrow or de- 

 pression. The hinge is nearly transverse. The whole surface is marked 

 with fine transverse striae, disposed concentrically on the convex part, 

 and expanding over the anterior side with an elegant sweep, terminate 

 on the hinge Hne. The ridges are distant, and vary in strength and 

 number, but seldom exceed six or eight on each valve. The longitudinal 

 depressions mentioned by Mr. Parkinson as affording a specific distinction, 

 are obscure in many instances, and altogether wanting in others. The 

 specimens are from 3 to 4 inches long, and 2-5 inches wide; the greatest 

 convexity of the united valves is 3-5 inches. 



Mr. Parkinson, " as a tribute of gratitude for the advantages afforded 

 to science by the classification of Lamarck, has affixed his name to the 

 present species*." 



Localities. Upper chalk, near Lewes, and Brighton. 



85. Inoceramus Brongniarti. Tab. xxvii. fig. 8. 



Equivalved, gibbous, transversely costated; anterior side angular, 

 acute ; posterior side flat, truncated ; hinge transverse, straight. 



* Geological Transactions, Vol. y. p. 55. 



