[ 215 ] 



XVIII. — Remarks on a Section of the Upper Lias and Marlstone of 

 Yorkshirey showing the limited vertical range of the Species of 

 Ammonites, and other Testacea, with their value as Geological Tests, 



Bv LOUIS HUNTON, Esq. 

 Communicated by J. F. Royle, Esq., F.G.S. 



[Read May 25, 1836.] 



On presenting a stratigraphical arrangement of the fossils in the lias forma- 

 tion on the coast of Yorkshire, I wish to offer the following remarks re- 

 lative to their geological distribution. 



The section (p. 221.) refers to that part of the coast between Whitby and 

 Redcar, in which the Loftus and Boulby Alum Works are situated, and was 

 named by General Mudge " Easington Heights." Its greatest elevation is 

 681 feet. It includes the inferior with a part of the great oolite series ; and 

 the lias is better developed in this place than in any other part of the coast, 

 the upper shale having a thickness of 200 feet, and the marlstone of 160; 

 and there are about 150 of the lower shale also exposed. 



With regard to the correctness and universality of the order given to the 

 fossils, the position of no one species was fixed till after several had been ex- 

 tracted from the situation indicated in the section, as well as in various differ- 

 ent localities from the Alum Hills, fronting the vale of Thirsk, to the peak 

 near Whitby; and in the majority of instances, from thousands of specimens 

 afforded by the quarrying of the lias shale in the manufacture of alum. 

 Though it would have been easy to have added many more species, the geo- 

 logical situation of which is determined, yet wherever the limits of distribution 

 have not been clearly defined, they have been omitted. 



Upper Lias Shale. — Commencing at the surface of this deposit, the first 

 fossil present in any quantity, is the Nucula ovum (see section, p. 22 1.); which, 

 after descending a few feet and entering what is technically called the " hard 

 or cement stone seam," occurs in great abundance ; but below that bed it 



