364 ITR. A. J. jrE:ES-BEOWNE ON A 



Humber continues throughout Yorkshire to Speeton, though rarely- 

 seen in place. Its occurrence has long been noticed, and Mr. C. Pox 

 Strangways * has taken it to mark the upper limit of the Lower 

 Chalk. The true position of this bed in Yorkshire as the zone of 

 Belemnitella plena is now for the first time recognized. 



The hase of the Middle Gliallc. — I also agree with Mr. Jukes- 

 Browne t in recognizing the rough creamy yellow chalk which 

 occurs between the zone of Belemnitella plena and the chalk with 

 flints as the condensed equivalent of the Melbourn Rock and Zone 

 of Rhynchonella Cuvieri. 



The occurrence of Inoceramus mytiloides, BJiyncJionella Cuvieri, 

 and Ecliinocoyius subrotimdus, the structure and rough character of 

 the chalk, suggestive of rearranged chalky material, always seen 

 at this horizon, and which is continued through Lincolnshire and 

 Yorkshire, identify it with the base of the Middle Chalk of the South 

 of England. The gradual approach of the Chalk with flints to the 

 Lower Chalk should be noted, and the value of the flints for strati- 

 graphical purposes may be estimated from the following : — at Dover 

 they are about 120 feet above the zone of Belemnitella plena ; at 

 Hitchin the first line of flints, followed by others at distant intervals, 

 occurs about 45 feet above the base of the Middle Chalk. In 

 Lincolnshire flints occur in regular lines and as close together as in 

 the Upper Chalk in the South of England, only 15 feet above the 

 Belemnite-marls, and this is reduced by nearly one half at Speeton, 

 where flints come on 8 feet above the Marls. Moreover, at Speeton 

 beds of flints some yards in extent occur as low as bed 4 in the 

 Chalk Marl. 



It will be seen from the foregoing that the divisions of the Lower 

 Beds of the Upper Cretaceous series of Lincolnshire and Yorkshire 

 are in harmony with those of the more southern counties, and that 

 the diff'erences which exist between my own reading of these strata 

 and that of those who have gone before me are matters of detail rather 

 than of fact. It was not possible to compare the Chalk-area north of 

 Hunstanton with that of southern England until the remarkable 

 changes which occur between Cambridge and !N'orth-west N'orfolk 

 were understood. But with the help of the recent work of Mr. 

 Jukes-Browne and myself, the correlation of the two areas can now 

 be made, and is, I think, satisfactorily established in the present 

 paper. 



Desceiption of a ktw Species of Holaster. 

 By A. J. Jueiis-Beowne, Esq., E.G.S. 



Holaster EOTxrifrDus, sp. nov. (Plate XII.) 



Descrij}tion. — Test large, rather thick, tumid, circular, or broadly 

 ovate, but generally as broad as long. Upper surface elevated and 

 sloping evenly all round towards the ambitus. Under surface 



* "Geol. of the country between York and Hull," Mem. Geol. SurA-ej, p. 29. 

 t " Geol. East Lmc," Mem. Geol. Survey, p. 29. 



