216 



MESSES. W. HILL AND A. J. JTJKES-33EOWNE ON 



17. The Melbouen Eock and the Zone of Belemnitella plena 

 from Cambeidge to the Chilteen Hills. By "W. Hill, Esq., 

 E.G.S., and A. J. Jukes-Beowne, Esq., E.G.S. (Eead February 

 10, 1886.) 



§ 1. Inteodfctoey. 



The Melbourn Eock was described by one of us in 1880 * as a band 

 of rocky cbalk occurring in Cambridgesbire at a distance of about 

 80 feet above the Totternhoe Stone, and forming tbe base of a 

 middle division of the chalk. Since then the outcrop of this rock 

 has been traced south-westward through the counties of Hertford, 



Eig. 1. — Diagram showing the usual outline of the face of an exposure 

 ivhere the Melbourn Hock and Zone of Belemnitella plena, are 

 seen. (Scale ^ in. to 1 ft.) 



Upper yellowish bed of 

 Melbourn Eock 



Lower whitish hard no- O '^_,-'^'' r .' y^-'- -^'J^j 



dular bed of Melbourn ■< ~>-'T* p'^'i'-' v* ^/ 



Upper Marly Eed 



Zone of I 

 Belemnitellai Hard White Bed 

 plena. 



Lower Marly Bed 



Lower Chalk 



* Geol. Mag. dec. ii. vol. vii, p. 248 ; and "-Geology of Oambridge," Mem. 

 Geol. Survey, p. 65. 



i 



