380 



situation for measuring beds and collecting fossils of the series. 

 Here the range and succession of the Ceplialoiooda can be well 

 observed. The Cefhalopoda are characteristically different in 

 the different strata. The Ammonites, for instance, occur in the 

 following descending order : — 



1. Ammonites annulatus {A. communis) .. .ahove the Ironstone 

 a. „ spinatus in the Ironstone 



3. „ margaritatus in the Marlstone 



4. ., maculatus{A.capricomus) below the Marlstone 

 and so on with the other species. 



Still pursuing the subject, we would refer to the more recent 

 observations of the Yorkshire geologists. "The Yorkshire 

 Lias " of Tate and Blake devotes 13 pages alone to the 

 discussion and description of the Spinatus Zone, and rightly so, 

 considering the interests involved, as all the workable beds of 

 liassic ironstone are confined to this part of the Middle 

 Lias. We might have readily quoted from the wealth of 

 information brought together by these authors in favoiar of our 

 views of this part of the Liassic series, but will avail ourselves 

 of the transcript, with the kind permission of the Eev. J. F. 

 Blake, M.A., F.G.S., of a single section of the numerous 

 examples, in order that the reader may fairly compare our beds 

 with the Yorkshire deposits of the same Zone. 



" THE YORKSHIRE LIAS," p. 130. 

 SECTION OF THE SPINATUS ZONE AT OLD NAB. 



