14 LIAS OF ENGLAND AND WALP.S : 
Cetiosauriis and Iguanodon are examples, are considered to have 
been dwellers on the land ; and in the Purbeck Beds we find 
Macellodus, the earliest Jurassic representative of the Lizards. 
Insects of all kinds have been found plentifully at certain 
horizons, in the Lower and Upper Lias, in the Stonesfield Slate, 
and in the Purbeck Beds. 
Land and Freshwater Mollusca occur in some divisions of the 
Oolites, and more especially in the Purbeck Beds ; their occurrence 
in the Lias, according to Mr. E. Wilson, requires confirmation. 
Kemains of land organisms are thus but scantily preserved, 
and the vertebrate remains are extremely rare even in those 
estuarine or fresh- water accumulations where we might expect to 
find them more commonly. There is, however, ground for hoping 
that they may be found eventually at localities and horizons other 
than those in which their remains have at present been discovered. 
Indeed, since these remarks were written, the first British 
Cretaceous Mammal has been discovered, in the Wadhurst Clay, 
near Hastings.* 
Insects, occurring as they sometimes do in purely marine 
deposits, were probably in such cases blown out to sea, or floated 
into the sea by rivers. Drift-wood and lignite occur at various 
horizons. Among the plant-remains, those of Cycads and Conifers 
are the more abundant forms. Ferns are not often preserved: 
many species originally described as ferns are now known to be 
Cycads. Dr. J. H. Balfour speaks of the Jurassic period as the 
reign of Gymuosperms. The first definite traces of Cycadece are 
recorded ; none of the forms obtained are very large, but the 
CojiifercB present arborescent types of the first magnitude.f 
Monocotyledons are occasionally preserved. 
Of the marine or partially marine forms of life many Reptiles, 
and especially the Ichthyosaurus and Plesiosaurus are characteristic 
(see Figs. 2-6, pp. 37-39). Recent researches tend to show that 
the former genus had a more extended caudal fin than is usually 
represented in figures.J Other Reptiles, more or less aquatic 
in their habits, are the Pterodactyls Dimorphodon and Rham- 
phocephalus the Crocodilians Tcleosaurus, Dacosaurus, and 
Steneosaurus ; and the Chelonia. No Snakes are known. The 
larger Saurians are more abundantly preserved in the Lias lime- 
stones and clays, and in the Oxford and Kimeridge Clays. 
The Fishes are well represented and include the Selachians, 
Hybodus, Acrodus, Stropkodns, Asteracunthus, and Squaloraja ; 
and Ganoids, such as Dapcdius, Pholidophorus, Leptolcpis, 
Lepidotus, and Mcsodon (Pycnodus). (See Figs. 811, pp. 40, 41.) 
They occur in various strata, but more especially in the lime- 
stones, including the oolitic beds, and in the shales. 
Of Mollusca we find the first traces in this country of 
Ammonites and Belemnites. They occur more or less abundantly 
* A. S. Woodward, Proc. Zool. Soc., 1891, p. 585. 
f Count de Saporta, Geol. Mag., 1872, p. 274. 
j Lydekker, Natural Science, 1892, p. 514. 
