, 1826.] tokich appear on the Yorkshire Coast. 357 



rough) were fragments of a small madrepore, fragments of shells, 

 serpulce, a small ostrea, traces of trigonia davellata, fragments of 

 penia aviculoides, &c. 4. At White-nab, south of Scarborough, 

 are some beds which contain many fossils, among which were 

 remarked, perna aviculoides, trigonia davellata (I), avicula, frag- 

 ments of a modiola, &c. 8i.c. 6. Among the beds associated 

 with the limestone of Cloughton Wyke were traces of a caryo~ 

 phyllia, resembling the great fossil of the coral rag, traces of a 

 trigonia, many casts of a mya (?), &c. 6. Among the calcareous 

 nodules derived from the shale beds near the bottom of the 

 formation east of Robin Hood's Bay, I remarked fragments of 

 ammonites, a.pecten, avicula [costata ?), mi/a (?). Near the same 

 place were beds of small oysters ; and in the coarse beds (f/ogger) 

 at the bottom of the formation were belemnites, and some other 

 obscure fossils in calcareous concretions ; and a trigonia, which 

 has sometimes been erroneously named davellata. 



These short notices appear to bear out the observations which 

 were made above. Unfortunately I have no opportunity of veri- 

 fying them ; but imperfect as they are, they may convey some 

 general notion of the manner in which the fossils are grouped iu 

 this interesting but anomalous formation.* 



Sect. 7. — Alum-shale. 



This immensely thick deposit, chiefly composed of slate clay 

 in different states of induration, begins to rise from beneath the 

 coarse sandstone near the eastern extremity of Robin Hood's 

 Bay. After ascending with great regularity for a few hundred 

 feet, it is interrupted at the Peak by a remarkable dislocation 

 which, on the south-east side of its range through the strata, has 

 produced a subsidence of at least 300 feet, and brought the 

 upper and middle beds of the formation into immediate contact. 



At the village of Robin Hood's Bay, the several beds are, by a 

 northern dip, brought down towards the beach ; and near Hawsker 

 Bottoms, the highest part of the formation appears once again 

 at the base of the cliff. From thence, in following the line of 

 coast, the strata are observed to make some considerable undu- 

 lations ; but the alum-shale is seen at ditferent elevations in 

 every part of the cliff as far as the south side of the entrance of 

 Whitby Harbour. There the strata are interrupted by q. fault 

 which ranges up the valley of the Esk, and produces such a 

 down-cast on the north side, that the alum-shale is thrown below 

 the level of the beach.f Near Sandsend it again rises, and in 



• Some excellent collections of fossils which have been formed by persons resident on 

 the coast, lose a great part of their value from the want of more precise information 

 respecting the localities from which the specimens are derived. 



+ Similar indications of great faults, ranging through our secondary strata in tlie 

 direction of the principal valleys by which they are intersected, are by no means of rare 

 occurrence. 1 have observed trtices of such _/(iu//j in almost every great valley, which 

 cuts through the magncsian liuiestonc ia its range from iS'ottingham to the mouth of the 



