THE JURASSIC SYSTKM 415 



and Ginkgo. Among this vegetation insects abounded, such as 

 bettles, flies, and dragon-flies. 



In tin- water lived molluscs of the genera Cyrena, Anodonta, 

 crocodiles of the Gavial type, and turtles (Protochelys). 



On land there were small marsupials, Amphitherium, Amphi- 

 < i/i if." 1 , Amphilestes, and Phascolotherium (Fig. 137), and the Protothere 

 Stereognathus. The huge Dinosauria, Megalosaurus and Ceteosaurus, 

 were also terrestrial creatures (see Fig. 136). 



C. THE MIDDLE JURASSIC OF ENGLAND 



Geographical Range. Like the Lias, the Middle Jurassic 

 Series ranges completely across England from Dorset to Yorkshire. 

 It occupies the Dorset coast between Bridport and Weymouth, 

 and runs inland by Yeovil, Sherborne, and Bruton to the Mendips. 

 In Gloucestershire it gives rise to the well-known scenery of the 

 Cotteswolds, and spreads over a considerable width of country. 

 Thence it passes through the counties of Oxford, Northampton, 

 Rutland, and Lincoln, forming the long escarpment known as the 

 "cliff" in Lincolnshire, which runs due north from Grantham by 

 Ancaster, Navenby, Lincoln, and Kirton to the Humber. 



In South Yorkshire it makes but little show, the beds being 

 thin, but north-west of Malton they thicken, and, sweeping round 

 to the north of Helmsley, form the high ground of the Yorkshire 

 Wolds, which range from west to east and terminate in the cliffs 

 between Whitby and Scarborough. 



The component members of this series in England are a variable 

 series of oolites, shelly limestones, ironstones, clays, and sands ; 

 none of the strata continuing long of the same thickness, and many 

 of them thinning out altogether within comparatively short 

 distances. The most persistent stratum is that which forms the 

 summit of the series and is known as the Cornbrash. In the 

 south of England, where the most complete succession of purely 

 marine deposits is found, the series has been divided into the 

 following groups and zones : 



Zones. 

 Cornbrash Clydoniceras discus. 



Bath Oolites 

 (Bathonian) 



Forest Marble Waldhtimia diyu.ut. 



Oaeloceras subcontractum. 



Great Oolite \ 



Fuller's Earth / 



.Clypeus and Trigonia grits Parkinsonia Parkinson*. 



fTerebratiila Beds Witehellia. 



Inferior Oolite f Gryphite and Trigonia grits Lioceras concavum. 



(Bajocian) I Freestones and Pea-grit Ludwigia Murchisc 



vOpalinum band Lioceras opalinum. 



