10 March, Morphogenesis of cerfaiii Pelecypoda. 



Fig. 2. 

 Diagram illustrating the origin of the undulate tvpe cf diagonal ornament. 

 XXX growth lines across ib.e diagonal ornament. 

 1, 3, 5. 7 radii. 



m\ ^ 



-Pig- 3- 

 - - - - Growth lines. 

 Diagrams illustrating the development of ornament. 



A. Concentric, due to intermittent activity of the whole mantle edge. 



B. Tuberculate concentric due to intermittent activit)- of the whole 

 mantle edge, augmented at certain spots. 



C. Tuberculate due to intermittent activity of definite parts of the mantle. 



D. Tuberculate radial due to continuous activity of the mantle at 

 definite points, and augmented intermittently. 



E. Radial, due to continuous activity of the mantle at definite points. 



F. Tuberculate diagonal due to waves of activity passing round the 

 mantle, and intermittently augmented. 



G. Diagonal, due to waves of activity passing round the mantle. 



H. Double diagonal, due to converging waves of activity, starting from 

 opposite ends of the mantle. 



