414 MR. S. S. BUCKMAJf ON [vol. IxXVlii, 



Diagram 10. — Non-local stratal repetition. 

 (N.) Gloucester. Dorset (S.) 



Scissum. Limestone. 



Limestone. 



29—27 Limestone 



26—24 Limestone. 



23—21 Limestone 



20-18 



17-15 



14-12 



Clay. 



hardly be supposed that these snnultaneous depositions of different 

 strata form an isolated case — in fact, there is every reason to think 

 that the phenomenon is rather frequent. It maj^ however, be 

 masked by paucity of exposures and b}^ hemeral sequences not having 

 been so fully Avorked out. In the case of paucit}'' of exposures, 

 faunal analyses of the contents of a formation should be made. 

 If they reveal notable discrepancies at certain localities, the 

 explanation may be sought in the phenomenon of sj^nchronous 

 deposition of different strata — the similar lithic character as 

 evidence of date should be regarded with suspicion. 



It is not surprising that, in the Midford Sand case, observers 

 disputed fruitlessly for many years as to the position of the Sands. 

 But the palaeontology of these observers was much at fault — a 

 name like Ammonites variabilis was applied to species of such 

 diverse genera as Haugia, FJilyseogrammoceras^ JPleydellia^ 

 Hammatoceras, Sonninia, and Fissilohiceras. 



I hope to be able to illustrate the phenomena of these Sands 

 and synchronous deposits moi'e fully in some subsequent paper of 

 this series — much of it is written. Meanwhile, I return to the 

 subject of stratal repetition, as illustrated b}'' the geographical 

 shifting of the focus of deposition (see Table III, p. 415). 



