EDITORIAL I9 



LIST OF SUBSTITUTED PLATES. 



Reason for substitution. 

 New photographs after removal of matrix. 

 Re-orientation of block [and better print ?]. 

 Change of name, identification with Sowerby's 



species having proved erroneous. 

 Better print : no other difference. 



Re-orientation of block and partial re-numbering 



of figures. 

 Better print and addition of fig. numbers. 

 Change of name and of hemera. 

 Correction of plate-number (incorrectly CLDIII). 

 Better print : no other difference. 

 Better print and slight correction in fig. numbers 



(IB). 



Change of name and of hemera. 



Change of name (pre-occupied) . Measurements on 



original omitted on reprint. 

 Cancelling of protograph reproductions. 

 Inversion of block. 

 Change of generic name and of hemera. Slightly 



modified wording of legend to 718B. 



In the cases of PI. 524 and 537, at least, it is advisable to retain 

 the original as well as the substitute. 



The author has himself indicated the several ways in which the 

 work may be arranged for binding (Vol. V, p. 5). For the purposes 

 of the working palaeontologist there can be no question that the 

 chronological arrangement is the best. Whatever changes of detail 

 may prove necessary in future, all contemporary species will be in 

 proximity. The only objection pointed out no longer holds since the 

 work is ended. It is suggested that a convenient division would be 

 into six volumes of plates, covering respectively the ages (1) Gigantitan 

 to Perisphinctean, (2) Cardioceratan to Macrocephalitan, (3) Clydoni- 

 ceratan to Stepheoceratan, (4) Sonninian to Grammoceratan, (5) Haugian 

 to Amaltheian, (6) Liparoceratan to Psiloceratan. Each such volume 

 would contain some 150 to 200 plates, and each separation comes at a 

 well-marked palaeontological change. A seventh volume would include 

 all the letterpress and the five portraits (two of J. Buckman, one each 

 of S. S. Buckman, M. Simpson and J. W. Tutcher). 



In arranging the plates on this plan, the two first of the tables 

 that follow will be useful. Table II will show where each plate should 

 go, and Table I will check the resulting assortment. It is suggested 

 that sheets of paper of two colours should be intercalated between the 

 plates, to mark off the several ages and hemerae. A similar intercalation 

 would be useful in the text-volume, to enable the Index of each original 

 volume to be found quickly. 



Whether bound in this way or bibliographically, the six tables 

 which follow should form a complete guide to the seven volumes. 

 Tables I, II, IV and V refer exclusively to the genera and species figured 

 on the plates ; in Tables III and VI others named in the text are also 



