ON THE BELEMNITES OF THE CHALK 

 OF YORKSHIRE. 



(plate XV.) 



By C. DAVIKS SHKRBORN', F.G.S. 



So far as at present known, the Belemnites found in the Chalk 

 of Yorkshire are Hmited to five forms — 



Actinocamax o-niiinla/its (De Blainville). Micrastcr cor- 



angtiinum zone to A. quadra/ us zone. 

 Actinocamax vcrus Miller. M. coi'-au_^uinum zone to A. 



quadratiis zone. 

 Actinocamax grossouvrci Janet. The subject of a special 



note by Mr. Crick (page 155.) 

 .Actinocamax plenus (De Bainville). A. plcnus zone. 

 Belemnites minimus (Sowerby ex Lister). Red Chalk. 



B. minimus, the common fossil in the Red Chalk, can easily 

 be found in those beds as exposed on the shore at low tide under 

 the Speeton Cliffs. The shape and lenj^th of this species \ aries 

 considerably with ai^e. 



A. pletiiis, lon^" known from the zone to which it g-ives its 

 name, from Lincolnshire to the South of Eni^land, has only 

 recently been found in Yorkshire. (C. Thompson, Naturalist, 

 July, 1905, p. 202.) 



A. verus, usually common in the Uintacrinus band of the 

 Marsupites zone in the South of England and for many years 

 known only from the top of the Micraster cor-auouinum zone of 

 Micheldever in Hampshire and Northfleet in Kent, was found 

 by Dr. Rowe in the same position at Walmer in Kent in 1903. 

 In Yorkshire, thoug-h rare numerically, it has a much more 

 extended range vertically, and Dr. Rowe and 1 hav^e collected it 

 on the Yorkshire coast from within fifty feet of the flinty chalk 

 of the Micraster cor-angu in u?n zone to the south of High Stacks, 

 right through the Marsupites and A. quadratns zones to within 

 25 feet of the highest part of the latter zone as exposed at 

 Sewerby Cliff. We did not, howexer, tind it in the successively 

 higher quadratns chalk as exposed in the pits between Sewerby 

 and Ruston Parva. Mr. Mortimer showed us an undoubted 

 example of this form, which he says came from the flinty chalk 

 of Fimber. This gives an undoubted range of 650 feet for A. 

 verus, a range in striking contast to that of 68 feet at Margate, 



