ZONE OF ARIETITES BUCKLANDI. 



41 



Horizons. 



Petrology. 



Palaeontology. 



Bucklandi -zone. 



Semicostatus, and 



Upper Bucklandi-beds. 



Scunthorpe Ironstone 

 beds, with 27 per 

 cent, ore, and having 

 a thickness of 27 feet. 



Arietites Bucklandi, A. Crossii, A. Conybeari, A. semi- 

 costatus, A. stellaris, Aegoceras Boucaultianum, Nau- 

 tilus striatus, Belemnites acutus, Pleurotomaria 

 Anglica, Cardinia gigantea, C. copides, C. crassissima, 

 Lima antiauata, L. gigantea, L. Hettangiensis, Pecten 

 texturatus, Gryphcea arcuata, Hippopodium ferri, 

 Cucullcea ovum. 



Bucklandi-zone. 

 Lower Bucklandi-beds. 



Lower limestone and 

 marl in Frodingham 

 Railway cutting. 



A. Bucklandi, A. Conybeari, A. semicostatus, Nautilus 

 striatus, Belemnites acutus, Cardinia Listeri, C. con- 

 cinna, Pleurotomaria Anglica, Lima antiquata, Pecten 

 textorius, Gryphcea arcuata, Lima gigantea, Phola- 

 domya ambigua, Unicardium cardioides. 



Angulatum 

 zone. 



Lowest Lias, Trent 

 Valley, 150 feet. 

 Dark shales and 

 clays. 



Aegoceras Liassicum, A. angulatum, Nautilus striatus, 

 Cardinia Listeri, C. concinna, Astarte obliqua, Pho- 

 ladomya prima, Cardita Heberti, Modiola nitidula, 

 Unicardium cardioides, Avicula decussata. 





Planorbis-beds and 



Avicula contorta series absent. 



Keuper. 



Red Marls. 



No fossils. 



In Yorkshire the Bucklandi-beds are exposed along the coast of Redcar and Robin 

 Hood's Bay. In both localities they are, however, at high flood-tide covered by the sea, 

 so that they are at all times studied with difficulty. Redcar affords the most complete 

 section, and this has been well worked out by Messrs. Tate and Blake in their able and 

 exhaustive work on the Yorkshire Lias. The sections I have given of these beds in the 

 midland and southern counties of England show that they are there composed of thick- 

 bedded blue hydraulic-limestones interstratified with beds of clay, bat in Yorkshire the 

 whole forms a " great argillaceous series, consisting of shales with shelly tops and thin, 

 earthy, and shelly limestones." 1 The Redcar rocks consist of two sets of scars or ledges, 

 separated by a broad expanse of a level pavement of shale. The scars succeed each 

 other at pretty regular intervals, have the general direction of east by north and west by 

 south, and are formed by the indurated tops of the shales. The inequality of the hard- 

 ness of the scars and shales makes the shore appear like a deep ploughed field at low- 

 tide. Their thickness is estimated at 180 feet, and they admit of a threefold division 

 based on the Petrology and Palaeontology of each series. Taking them in ascending 

 order from the Angulatum-beds we have following series — 



1 ' Yorkshire Lias,' p. 54. 



G 



