2/6 JURASSIC. 



In some localities, however, the Ammonites are irregularly 

 distributed in the Upper Lias. In thickness this formation varies 

 from about 5 to 230 feet. 



The Upper Lias in Dorsetshire is represented by a clay-deposit, 

 about 70 feet in thickness, which rests on the remarkable junction- 

 bed before noticed (see p. 271); the beds are well shown in the 

 clifts at Thorncombe Beacon. (See Fig. 40, p. 252.) 



The Upper Lias in Somersetshire is sometimes not more than 

 eight or ten feet thick, and it consists of thin beds of pale-grey 

 marly clay, and rubbly and nodular limestones, which are some- 

 times septarian. The most remarkable bed is the Saurian and Fish- 

 bed, consisting of nodular yellow limestone, which has yielded 

 beautiful remains of Ichthyosaurus, Telcosaurus, numerous Fishes, 

 Cephalopoda, Insects, and Crustacea. This bed has been observed 

 in the neighbourhood of Ilminster. The Cephalopoda include the 

 genera Geoteiithis and Teuthopsis. The softer parts of these cuttle- 

 fishes have perished, leaving only the internal cuttle-bone, in 

 the centre of which the ink-bag is usually found, still charged 

 with its black pigment. Attention was drawn to this Saurian and 

 Fish Bed by Mr. Charles Moore, who observed that the shape of 

 the nodule conforms roughly to that of the enclosed organism. 

 Beneath the Saurian and Fish zone come the Leptcena-beds, 

 characterized by the presence of Leptana IMoorei, and L. {Konmck- 

 ella) Bouchardii. ^ Similar Leptaena- and Fish-beds have been 

 observed at Churchdown Hill, Gloucestershire, bj' Dr. F. Smithe.^ 



There are many quarries showing Upper Lias near Ilminster, 

 South Petherton, and Yeovil. The beds occur at Pennard Hill, 

 Glastonbury Tor and Brent Knoll, and they have been detected 

 here and there in the Oolitic escarpments between Yeovil and 

 Bath, and at Dundry Hill. (See Fig. 39, p. 250.) 



In Gloucestershire the Upper Lias varies from about 10 feet at 

 Wotton-under-Edge (see Fig. 44) to about 300 feet at Cleeve Cloud, 

 and 380 feet at Bredon Hill, near Cheltenham. The thickness is 

 at Stroud 30 feet, Nailsworth 105, and at Birdlip 200. In Oxford- 

 shire the Upper Lias is sometimes very thin, being about 8 feet at 

 Fawler and 10 feet at Charlbury ; in places it is 40 feet, but it 

 probably does not extend far to the south-east beneath the newer 

 rocks in that area. In Leicestershire the thickness is about 

 300 feet; in Northamptonshire ('Blue Marl') it varies from 150 

 to 200 feet ; and in Lincolnshire the thickness diminishes to 

 60 feet. 



In Northamptonshire the Upper Lias may be seen at Milton, 

 Eydon, Towcester, Middleton Cheney, Byfield, etc. It is exposed 

 in the valley of the Nen and its tributaries at Bugbrook.^ The 

 lowest beds consist of finely-laminated shales (Paper-shales), with 



1 Moore, Proc. Somerset Arch. Soc. xiii. 119. 

 ^ Proc. Cottesw. Club. vi. 354. 



^ Brodie, Proc. Cottesw. Club, ii. 132 ; Beeby Thompson, The Upper Lias 

 of Northamptonshire (Northampton Museum Report), Midland Nat. ix. 121. 



