4 



Editorial 



Part xix of Type Ammonites, commencing Vol. Ill of the series, 

 is now presented to subscribers. The courtesy of Mr. T. Sheppard, 

 M.Sc, F.G.S., allows the addition of a portrait of Martin Simpson which 

 has appeared in Proc. Yorksh. Geol. Soc. XIX, 1918, xxxv. This has 

 not now been headed, so that subscribers may place it as a frontispiece 

 to whichever volume of the series they choose. 



As in the present volume the text must be very strictly limited, 

 it is intended to supply deficiencies of description by detail (diagrammatic 

 and otherwise) in the illustrations. This has the advantage of not only 

 inducing greater strictness of observation, but of presenting the results 

 pictorially, that is, in a language which is universal. If the plates them- 

 selves were perfect they should, with their legends, give all necessary 

 details : descriptions should be superfluous. There will, however, be 

 descriptive matter ; but it will be held until depicted species have 

 accumulated. 



The legend of the plate is designed to give the following information : 

 name or other identification ; status as type, if it has such ; references 

 to protolog and protograph or other bibliographic details ; locality and 

 horizon according to original information — in quotation marks ; collection; 

 proportional formula ; see Q.J.G.S. LXXIII, 1919, 315. At foot of plate 

 will be given present name, presumed date and status. The date is to be 

 read as — age, in Roman, hemera, in italic type. This dating system 

 accords with a very detailed scheme, not yet complete : the Liassic portion 

 is given in the Journal cited above, but even that may require elaboration. 

 Two hemeral names with / between them imply that the species possibly 

 occupied an intermediate date, which may be added in brackets. 



Terminology 



In the legend is a further innovation — there is given in millimetres 

 as " max. c. xyz " the presumed maximum size of the specimen with 

 complete body-chamber added ; this within square brackets indicates 

 information from another, a more complete, example. 



This information prepares for a scheme of recording the great varia- 

 tion which adult Ammonites make at different dates in regard to size — 

 from a few to several hundred mm. Thus there are certain dates when 

 Ammonites of large size flourished, and others when small forms lived — 

 the maxima rising and falling like waves ; and there are further cases 

 of large and small Ammonites occurring in the same stratum — the 

 juxtaposition may not necessarily imply synchronism. 



In connexion with these data a concise Terminology is necessary, 

 particularly in regard to small Ammonites. Specimens may be small 

 as a matter of growth ; but they may also be small because they have 

 been reduced (1) by breaking off of outer whorls before deposition, 

 (2) by similar breakage in the process of extraction, (3) by both causes 

 combined. In practice it may seldom be possible to say which of these 

 causes has operated ; but distinction could be made by qualifying the 



