250 STATHER : BELEMNITES OF THE YORKSHIRE CHALK. 
base, A\ith the aid of Mr. Lamplugh's paper it has been possible 
to locate definiteh^ the exact stratigraphical position of each 
specimen. In aU, examples have been obtained from fourtfer 
different horizons, as shown on the accompanying table. Thes: 
represent, so far as is now known, a complete series from the lowes- 
Belemnite-bearing beds (of this ty^e) in the Upper Chalk to the 
highest, and without exception they all conform to the rule laid 
dov^Ti by M. Grossouvre. 
In fact, to such an extent is this the case that it is now 
easily possible to assign to its relative position in the series any 
particular specimen merely from the depth of its alveolar cavity 
alone. 
The illustrations shown on the Diagram clearh^ indicate the 
deepening of the alveolar cavity as we examine the specimens in 
descending order. I am indebted to Mr. W. H. Crofts for the draw- 
ings, and also to different members of the Hull Geological Society 
for the loan of specimens, all of which confirmed the results 
arrived at by an examination of my own specimens. 
