24 LIAS OF ENGLAND Al>L WALES: 
what is now Devon and Cornwall. In West Somerset, where the 
Lias approaches the Devonian rocks near Watchet and Porlock, 
it does not present conglomeratic conditions. Its relations with 
the old rocks where in contact, suggest faulting, and that the 
Quantock and Foreland ranges formed no part of the land-area 
in Liassic times.* 
In Monmouthshire the Lias presents its ordinary characters, 
dipping away somewhat abruptly from the present margin of Old 
Red Sandstone : so that formerly it may have stretched much 
further west. We have no indication there of marginal deposits. 
The Severn valley and the plain stretching towards Chester must 
have been covered by Lias continuous with that of the rest of 
England. Referring to the Jurassic rocks of Cumberland, both 
Mr. J. G. Goodchilu and Mr. J. E. Marr have remarked that 
there is no reason why these and newer Mesozoic rocks should 
not at one time have extended over the area now known as the 
Lake District, t 
In the south-east of England we know that the Lias does not 
extend beneath London, nor has it been found in any deep borings 
between the metropolis and Harwich. It occurs beneath Peter- 
borough and Oxford, and must terminate underground towards 
the south-east, somewhere between the sites of those cities and 
Harwich, Ware, London and Richmond. We can form no idea 
of its extent uncfer Hampshire and Sussex, although the evidence 
at our command suggests that in parts of the south-east of England 
the Lias is banked up against an old coast-line of the PaJseozoic 
rocks, and is overlapped by the Oolitic Series. 
Organic Remains. 
The Lias as a whole is rich in organic remains, and these for 
the most part are well preserved. The large Sauriaris dominated, 
and hence the period has been designated the Age of Reptiles or 
Saurozoic Epoch. Chief among these are the Ichthyosaurus, 
Plesiosaurus (see Fig.. 2-7, p. 37), and Dimorphodon (Ptero- 
dactyl). Some tiny examples of Ichthyosaurus have been found 
within the pelvis of parent forms, leading to the conclusion that 
the animal was viviparous. J The Fishes include many genera, 
such as Acrodus, Dapedius, Euynathus, Hybodns, Leptolepis, 
Pachycormus, and Pholidophorus. (See Figs. 811, pp. 40, 41.) 
Most abundant, and geologically speaking most important, are 
the Mollusca. In this country we find the first evidence of Am- 
monites and Belemnites, and of other genera such as Alaria, 
Amberleya, Nerita, Exoyyra, Gresslya, Goniomya, Homomya, 
Hippopodium, Opis, and Trigonia. The more abundant Gastero- 
pods are Cerithium, Plcurotomci.ria, Trochus, and Turbo. Car- 
* See also De la Beche, Mem. Geol. Survey, vol. i. pp. 250, &c. ; and Ussher, 
Proc. Somerset Arch. Soc., vol. xxxv. section 4, on Geol. map of West Somerset. 
f Trans. Cumberland Assoc., No. xiii. p. 95; and Geol. Mag. 1889, p. 154. 
J J. Chaning Pearce, Ann. Nat. Hist., vol. xvii. p. 44 ; Seeley, Rep. Brit. ASROO. 
for 1880, p. 69. 
