Manchester Memoirs, Vol. h. {i<^i\),No. \^. 5 



The second and more accentuated bend marks the 

 introduction of that part of the ornament which more 

 nearly approaches the concentric, that is, follows more 

 closely the line of growth. It occurs in that part of the 

 flank in which the growth lines bend sharply upward to 

 run parallel to the anterior edge, and where they are 

 also rapidly closing up. This upward bend causes the 

 concentric ornament and consequently the tubercles in 

 that part of the shell which it affects to be carried upward. 

 So that if A, B, C, D, E & F represent the tubercles of a 

 diagonal row above the bend, and G the tubercle after the 

 beginning of the bend upwards, G will not lie in the 

 straight line AF, but slightly above it in such a way that 



Fig. 4- FtS- 5- 



Showing the development of appa- Showing a double bend on an 

 rently concentric diagonals, elongated 7\ clavellala. 



owing to uplift. 



the line will have to bend up to reach it, as in Fig. 2 and 

 also in Fig. 4. The continued uplift may cause the 

 succeeding tubercles of a diagonal row to lie at the same 

 level as, or even above their predecessors, thus forming a 

 horizontal, or even an upcurved line which forms an acute 

 angle with the upper portion. If the uplift is great 

 enough apparent concentricity may be attained by the 

 diagonals. 



