LIST OF PLATES. 



PLATE I. 



Illustrative of the Report upon the Channels of the River Mersey. 



PLATE n. 



Illustrative of the Dredging Report. — Frith of Clyde. 1856. 



PLATE in. 



Illustrative of Photochemical Researches, by Professor Bunsen and Dr. 

 Henry Roscoe. 



PLATES IV. and V. 



Illustrative of Mr. William Fairbairn's Report on the Tensile Strength of 

 Wrought Iron. 



PLATES VL to IX. 



Illustrative of Mr. P. P. Carpenter's Report on the present state of our 

 knowledge with regard to the Mollusca of the West Coast of North 

 America. 



Plates VI., VII., VIII., IX. are designed to illustrate variations of form 

 between individuals of the same species, observed in comparing large 

 numbers of specimens from the Reigen Collection of Mazatlan Shells : vide 

 Report, pp. 241-264. 



PLATE VI. 



Fig. 1. Three adult specimens of Area grandis, Brod. & Sby., laid on the same hinge- 

 line: n, normal state; e, elongated; o, obese. 



Fig. 2. The same specimens in profile. 



Fig. 3. Two young specimens, showing that the changes of form are not merely the 

 result of circumstances of growth : e, elongated ; t, transverse. 



Fig. 4. The same specimens in profile. The A. eequilatera, Sby., is probably the 

 young of this species. It has been selected from a group usually constant 

 in its characters ; the nestling Byssoarks being notoriously irregular. 



