334 JURASSIC. 



and clay ironstone near the base. The name was adopted by 

 Conybeare and Phillips in 1822; and the term Kimeridgian was 

 subsequently used by D'Orbigny. The name is taken from Kime- 

 ridge, in the so-called Isle of Purbeck, where the beds of bitumi- 

 nous shale have been used as fuel, and called Kimeridge Coal ; and 

 where the dark cliffs form striking features in the coast scenery. 

 (See Fig. 45.) The thickness is upwards of 600 feet in Dorsetshire, 

 about 500 feet near Swindon, only 100 feet near Oxford, but 

 upwards of 500 feet in Yorkshire. Prof. J. F. Blake has divided 

 the Kimeridge Clay into two sections ; the upper of which consists 

 of paper-shales, bituminous shales, and cement-stones, with a 

 maximum thickness of 650 feet or more; and the lower of blue 

 sandy clay with ferruginous concretions or 'doggers,'' having a thick- 

 ness of from 300 to 500 feet, typically developed in Lincolnshire; 

 but the greatest developments of these sections are not knoiuii in the 

 same area. Near the junction with the Corallian series the beds 

 become sandy and the line of demarcation is indistinct. 



Palceontologically the Kimeridge Clay on the Continent has been 

 divided as follows :' — 



Upper. — Virgula beds, with Exogyra virgula. 



Middle. — Pteroceras beds, with Pteroceras Oceani. 



Lower (passage-beds). — Astarte beds, with Astarte supracorallhia. 



Prof. Blake has not definitely recognized the Middle zone in 

 England, although he identifies the Virgulian and Astartian beds.'^ 



Amongst the fossils are Exogyra {Gryphcea) virgula, E. nana, 

 Ostrea dcltoidea (abundant in the lower beds), Cardiutn striatulum, 

 Astarte supi-aco7-allina, A. lineata, A. ovata. Area rhomboidalis, Thracia 

 {Panopcea) depressa, Pecten nitescens, Liicina minuseiila, Pleiirotomaria 

 reticulata, Trigonia Voltzii (and other species), Rhynchonclla ijicon- 

 stans, Discina {Orbicula) latissinia, Lingula ovalis, Belemnites ex- 

 cent ricus, B. explanatus, B. nit id us, B. ahhreviatus. Ammonites hiplex, 

 A. mtitahilis, A. triplex, with the problematical ^/>/;'(r/// or opercula 

 called Trigonellites, of which T. latus is abundant east of Kimeridge ; 

 also Serpula tetragona, S. intestinalis, a few Crustacea, Echinoder- 

 mata, and many Foraminifera. 



Saurian remains have been found in many localities, they include 

 Ccteosaurus, Dakosaurus, Omosaurus, Pterodactylus, Plesiosaurus, 

 Pliosaurus, Ichthyosaurus, Steneosaurus, Telcosaurus, etc. Testudinate 

 remains also occur, Pelohatochelys, etc. The Fishes include Astera- 

 canthus, Gyrodus, Lepidotus, Pycnodus, etc. 



Mr. Hudleston has remarked that there is no formation in the 

 whole Jurassic system, as developed in England, which is more 

 difficult to tabulate or understand than the Kimeridge Clay,^ for 

 the palceontological divisions made in one locality do not seem 

 to correspond with those in another. In Dorsetshire the Lower 



1 Oppel, Die Juraformation. See also Dr. C Struckmann, G. Mag. 1881, 



P- 556. 



- Q. J. xxxi. 196. See also Judd, Q. J. xxiv. 239. 



3 Reports of sub -committees Inteniat. Geol. Congress, Cambridge, 1S85, p. 88. 



