Sherborn: On the Bclcmnites of the Chalk of Yorkshire. 153 



which, so far as is known at present, is the g"reatest measured 

 thickness for this Belemnite in the South of Eng-land. 



A.grmuilatiis, known only from the upper part of the Micras- 

 ter cor-angninuni zone at Gravesend in Kent, passes throug"h 

 the Marsiipites zone, where it is common, and occurs somewhat 

 abundantly in the lower 150 feet of the A. quadratus zone in the 

 South of Engfland. In Yorkshire, not only is it found in the 

 flinty base of the M. cor-anguinum zone at Fimber (Mortimer : 

 See Rowe, Proc. Geol. Assoc, XVIII. (4), 1904, p. 270), but 

 Dr. Rowe and I have traced it rig-ht through the remainder 

 of this zone on the Yorkshire coast, up through the zone of 

 Marsiipites to the top of the highest quadratus chalk as exposed 

 at Sewerby. Further than this, we have followed it successively 

 throug'h the higher beds of this zone from Bessingby to 

 Carnaby, Burton Agnes and Ruston Parva, thus demonstrating" 

 an unbroken range in Yorkshire for this form of about 800 feet, 

 or nearly five times as great a rang^e as known in Sussex, 

 hitherto the greatest known. Moreover, throughout the whole 

 of this great thickness it is clear that it is only one form, and 

 the slow evolution of the species can be traced, step by step, 

 until at last we are at the point, so to speak, of the next form, 

 the so-called species Actinocainax quadratus, which g"ives its 

 name to the zone. But a true specimen of the deep and quad- 

 rate alveolated form known as A. qjiadratus has not yet been 

 found in Yorkshire ; and if, as is probable, that Ruston Parva 

 gives us the highest part of the quadratus zone which has 

 escaped denudation in the county, it never will be found, for the 

 true quadratus occurred in the hig'her beds which have long* 

 since been destroyed 



For further particulars of Yorkshire Chalk Belemnites, that 

 is the two latter forms, the reader must refer to the paper 

 mentioned above (Rowe, Proc. Geol. Assoc, XVIII. (4), 1904, 

 pp. 193-296), where the whole of the White Chalk and its fossils 

 of the Yorkshire coast is described. I reproduce here the figure 

 and legend there given of the alveolar ends of A. granulatus, 

 showing the progressive deepening of the alveolar cavity as 

 the belemnite ascends in the zones. I also give figures of the five 

 forms discussed for handy reference (plate XV.), and call 

 attention to a remarkable deformed specimen of A. granulatus 

 described by Mr. Crick in an appendix to Dr. Rowe's paper, 

 and reproduced in the ' Naturalist' for May, 1904. 



1906 May I. 



