278 



JURASSIC. 





5= a 



S O C nl rt 



u 't; t f^ ^ 



L^ >< O ^ V-1 



The cliffs near Whitby, from three to four hundred feet in height, 

 are partly composed of dark grey beds of shaly clay (Whitby shale), 

 lying nearly horizontal, and stretching out at the base into an ex- 

 tensive flat pavement, on which the sea washes, and which is laid bare 



to a considerable distance at low 

 water. In the lower "Grey Shale" 

 A. anmilatus is abundant in nodules 

 of ferruginous and argillaceous lime- 

 stone ; A. cornucopia also occurs. 

 Although the characteristic Ammo- 

 nite is essentially an Upper Lias 

 form, this division has been placed 

 with the Middle Lias by Messrs. 

 Tate and Blake, because A. margari- 

 tatus and other IMiddle Lias fossils 

 occur also in it. The beds are ex- 

 posed in Runswick Bay, south of 

 Staithes, in West Arncliffe, etc. (See 

 p. 273.) The Jet-rock series com- 

 prises hard shales with A. serpen- 

 tiniis, A. heterophyUus, and hioce- 

 ramiis dubius, also lenticular masses 

 of stone like huge cheeses ("cheese 

 doggers"), and hard blue bitumi- 

 nous shale, 20 feet (the Jet-rock), 

 containing jet in the interstices be- 

 tween the layers, in thin lenticular 

 masses. " These shales are in 

 places so highly impregnated with 

 iron pyrites and bitumen that spon- 

 taneous ignition is not of infrequent 

 occurrence ; such natural fires have 

 been burning for years at Staithes, 

 Lofthouse, etc." ^ The Jet-rock may 

 be well studied on the coast near 

 Saltwick Nab, south of Whitby ; also 

 between Sandsend and Kettleness, 

 hence the name Sandsend Beds of 

 Young and Bird. Many fossils 

 have been obtained on the shore 

 at Runswick. Remains of Reptiles 

 and Fishes are not uncommon, the 

 "scale-fish," Lcpidoius semisn-ratus, 

 being most characteristic. Jet has 



^ Tate and Blake, Yorkshire Lias, pp. 

 173, etc. ; Phillips, Geol. Yorkshire, part I. 

 edit. 3 ; Louis Hunton, T.G.S. (2), v. 215 ; 

 W. C. Williamson, Ibid. 223; M. Simpson, 

 Fossils of the Yorkshire Lias, edit. 2, 1S84 ; 

 Explan. of Sheet 95 N.W. (Geol. Survey), 

 by C. F. Strangways and G. Barrow. 





