01KIANIC REMAINS. 25 
dinia, found also in the Rhaetic Beds, is especially characteristic 
of the Lias.* Many of the Mollusca date from the Trias and some 
from earlier periods : there are few genera of Gasteropoda or 
Lamellibranchs peculiar to the Lias, but among the former, 
Cryptcenia may be mentioned. 
Brachiopoda are abundant ; we find the last representatives of 
the Palaeozoic forms of Lepteena, and Spiriferina ; while Tere- 
bratella, Zcllania, &c. appear for the first time. Crustacea of the 
genera .Eryon, dSffer, Glyphea, &c. are found, and some species 
are not uncommon. Of the Arachnida, one doubtful example of 
an aquatic Spider has been recorded. 
Insects, or remains of them, are plentiful at certain horizons. 
None of the forms are very distinct from those now in existence. 
They include Orthoptera, Diptera, Neuroptera, Coleoptera, and 
Rhynchota (Hemiptera) ; and they indicate a temperate climate. 
Crinoids such as Pentacrinus and Extracrinus are locally 
abundant. In some cases the stems of Extracrinus exceed 
50 feet in length. Some forms of Echini such as Cidaris and 
Hempedina, and of the Coral Montlivaltia, are plentiful in places : 
but as a rule Echini, Polyzoa, and Corals are rare. Many Fora- 
minifera have been recorded. 
Lignite is met with here and there, and some plant-remains 
belonging to the genera Pachyphyllum (Araucarites\ Otozamites, 
&c., have been found. On the whole the Cycadaceae appear to 
have been more abundantly preserved than other plant-remains. 
Zones. 
A study of the fossil contents of the Lias has led palaeontologists 
to make certain divisions or " zones," based upon the succession 
of the organic remains. 
That certain groups of fossils characterize successive stages in 
the Lias was pointed out by Louis Hunton in 1836. His obser- 
vations applied to Yorkshire, where he was followed by W. C. 
Williamson and others. | In the south of England the sequence 
was noted in 183J) by De la Beche,J in 1840 by Strickland, and 
in 1842 by James Buckman.|| It was not, however, until after 
1856, when Oppel published his " Juraformation," that any 
systematic attempt was made to define and follow out these sub- 
divisions in our country. The work of Oppel was based on that 
of Quenstedt, yet he not only amplified our knowledge of the con- 
tinental strata, but showed that the main palaeontological divisions 
were applicable to this country. His work has been followed up 
by that of Thomas Wright^! and many others. 
* See also K. Tate, Geol. Mag. 1871, p. 5. 
f See C. Fox-Strangways, Jurassic Rocks of Yorkshire, p. 16. 
I Report on the Geology of Cornwall, &c., p. 227. 
Proc. Geol. Soc., vol. Hi. p. 315 ; Trans. Geol. Soc., ser. 2, vol. vi. p. 552. 
|| Moxon's Geologist, p. 16; Geol. Chart of the Cotteswold Hills, 1843; Murchi- 
son's Geol. Cheltenham, Ed. 2. pp. 41, &c. 
1" Quart. .Tourn. Geol. Soc., vol. xvi. p. 41 1. 
