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rock -bed of an impure Limestone, weathering brown, but blue in 

 the interior. In the eastern part of the county it is highly- 

 ferruginous, and varies from 1 to 10 feet in thickness. The 

 rock-bed forms the surface of several tabulated promontories, as 

 at Gretton, Bredon, Churchdown, and Stinchcombe Hills ; and 

 which produce fine picturesque effects in the physiographical 

 features of the western escarpment of the Cotteswold range. 



5. — The zone of Ammonites spinatus forms the upper portion 

 of the Marlstone in this district, and raust be studied in 

 connection therewith. At Leckhampton Hill the Marlstone 

 series is 115 feet thick, and this is its estimated thickness 

 in general around the western flanks of the Cotteswolds. It 

 may be studied at Chipping Campden, Stow- on-the -Wold, and 

 Ebrington Hill, which formed the northern promontory of the 

 ancient coast line. 



The Marlstone attains a great development in Yorkshire, 

 and is fully exposed in the fine coast section near Staithes, 

 and at Boulby Cliff; the grandeur of this section can only be 

 realised by the pedestrian, who at ebb tide sets about its 

 exploration, and examines at low water mark the vertical wall 

 of rock, built up of so many courses or zones of the Lias beds. 

 Many of the Brachiopoda, Conchifera, and Gasteropoda, from 

 the underlying zones of the Middle Lias, lived in the ocean 

 from whence the Marlstone was deposited ; but besides these 

 species other forms appear to be special to it, of which the 

 following may be enumerated : — 



Cephalopoda. 



Ammonites margaritatus, Montf. Ammonites heterophyllus, Quenst. 

 II Engleliardti, d'Orb. " Amaltheus, Scldoth. 



II Normanianus, d'Orh. " spinatus, Brug. 



•I fimbriatus, Soiv. Belemnites breviformis, Ziet. 



ECHINODEEMATA. 



Hemipedina Jardinii, Wr. Ophioderma Egertoni, Brod. 

 Uraster carinatus, Wr. » carinata, Wr. 



Astropecten Hastingiae, Forh. •> tenuibrachiata, Wr. 



Ophioderma MaUeri, Thil. Ophiolepis Murravii. Jbrft. 



