246 
NOTES ON THE BELEMNITES OF THE YORKSHIRE . CHALK. 
BY J. W. STATHER, F.G.S. 
In the Bulletin de la Societe Geologique de France for 1899, 
page 129, M. A. de. Grossouvre has an interesting paper^ on 
General Observations on Belemnites and particularly those of 
the Cor bier es district.'" 
In this paper the author seems to have been the first to have 
noticed the fact that, as the Belemnites ascend the strata, they 
gradually vary, both in the depth of the alveolar cavity, and in the 
nature of the granular surface of the guard. He points out that 
in the lower beds of the strata the alveolus is exceedingly shalloAV, 
and in fact hardly present at all ; as is the case in our Yorkshire 
and Lincolnshire examples of the ^ ell-known Belemnitella plena, 
which occurs at the base of the Middle Chalk, and can be said to 
have had no alveolar cavity at all, at any rate in that part which 
is preserved in the " Black Band." 
The next in ascending order, referred to by M. Grossouvre, 
are the forms known as Actinocamax westphalicus. which have an 
exceedingly shallow alveolar cavity, but which, so far, has not 
been identified in the Yorkshire Chalk. Still higher, the author 
refers to Act. graiiulatus, where the alveolar cavity is obviously 
deepening, whilst in the upper beds of the Chalk the cavity is 
distinctly quadrate in section, is much deeper, and quite typical 
of the form of Belemnite known as Act. quadratus. 
M. Grossouvre takes pains to point out in his paj^er that 
there is no distinct l:>reak in the sequence, but that westphalicus 
gradually merges into granulatus, and granulatus into quadratus y 
and that mtermediate forms obtain ^^'hich it is difficut to assign 
either to one species or the other. 
Dr. A. W. Rowe in his well-known series of papers on the 
English Chalk, showed in his Dorset memoir^ that, as in the case 
of France and Switzerland. ' we have (in Dorset) a complete and 
unbroken transition from Actinocamax westphalicus, with its 
notably shallow alveolar cavity, to the deeply alveolated Actino- 
camax quadratus." Dr. Rowe had the advantage of a perusal of 
M. GrossouxT:'e"s paper, and was gratified at being able to confirm 
the observations of that writer. 
1 Quelques Observations sur les Bdleninitelles el en pai ticulier ^ur cclles des Corbieres. 
2 Proc. Geol. Assoc., Vol. XVII., Pt. 1, 1901. 
