fro'^n Millstone Grit, N. Yorkshire. 



391 



The limestone bed is a little over 500 feet above the base of the 

 Millstone Grit as defined in the above-mentioned memoir.' 

 Mr. J. Pringle has kindly identiBed the fossils from these beds, and 

 has drawn up the following list : — 



Athyrid. 



Chonetes laguessiana, de Kon. 

 Ch. sp. (papilionaceous var.). 

 Lingula squamiformis, Phill. 

 Martinia glaber (Mart.). 

 Productus cf. longispinus, J. Sow. 

 P. sp. {semireticulatus ^xow"^) . 

 Schizophoria resujnnata (Mart.). 



Spirifer hisulcatus, J. de C. Sow. 



S. sp. 



Posidoniella Icevis (Brown). 



Pseudaviusium fibrillosmn (Salter) . 



Glyphioceras bilingue (?) (Salter) . 



Orthoceras sp. 



Cladodus mirahilis (?), Ag. (tooth). 



These specimens are now in the Jermyn Street Museum, the 

 registration numbers being Z 33H-74. 



Mr. R. Gr. Carruthers has sliced several Corals, which were obtained 

 from the highest limestone bed, and has identified Zaphrentis costata 

 and Z. constricta ; tlie latter, he remarks, occurs normally in the Lower 

 Limestone group of (Scotland. 



2. Calcareous 2. ^=^ 

 Shale. 



3. Thin Limestones 



and 



Calcareous Shales. 



4. Massive Limestone Bed. 



5. Calcareous Shale. ^ 



6. Blue Muddy Shale. 6 



Vertical Scale. 

 Fig. 1.— Section at Great Shunner Fell Well, Yorkshire. 



A list of fossils, chiefly only with the generic names, is given in the 

 Geologi(;al Survey memoir,^ but the specimens are not preserved in 

 the Survey collection. 



The Millstone Grit underlying the calcareous beds of this area, 

 although mainly comprised of grits and sandstones, and containing the 

 Tan Hill coal and other thin seams, is essentially a marine formation, 

 since many of the grits contain casts of Spirifer and Criuoids. The 

 strata were evidently formed rapidly in a sinking area, and the 

 change in character of the beds, resulting in calcareous deposits, may 

 be due to failure in the supply of coarse material, aided by an 

 increased depression of the area. As a result of this change to clearer 



' The Geologxj of the Country around Mallcrstang, etc., 1891, pp. 11-12. 

 2 Ibid., p. 160. 



