364 
ELEMENTS OE GEOLOGY. 
wood-eating and herb-devouring beetles, of the Linnean gen¬ 
era Elater^ Carabus^ etc., besides grasshoppers {Grylhis)^ and 
detached wings of dragon-flies and may-flies, or insects refer¬ 
able to the Linnean ^euev^Libellula^ Ephemera^ Hemerobius^ 
and Panorpa^ in all belonging to no less than twenty-four 
families. The size of the species is usually small, and such 
as taken alone would imply a temperate climate; but many 
of the associated organic remains of other classes must lead 
to a different conclusion. 
Fossil Plants. —Among the vegetable remains of the Lias, 
several species of Zamia have been found at I^yme Regis, 
and the remains of coniferous plants at Whitby. M. Ad. 
Brongniart enumerates forty-seven liassic acrogens, most of 
them ferns; and fifty gymnosperms, of which thirty-nine are 
cycads, and eleven conifers. Among the cycads the predomi¬ 
nance of Zamites^ and among the ferns the numerous genera 
with leaves having reticulated veins (as in Fig. 349, p. 349), 
are mentioned as botanical characteristics of this era.* The 
absence as yet from the Lias and Oolite of all signs of dicot¬ 
yledonous angiosperms is worthy of notice. The leaves of 
such plants are frequent in tertiary strata, and occur in the 
Cretaceous, though less plentifully (see above, p. 303). The 
angiosperms seem, therefore, to have been at the least com¬ 
paratively rare in these older secondary periods, when more 
space was occupied by the Cycads and Conifers. 
Origin of the Oolite and Lias. —The entire group of Oolite 
and Lias consists of repeated alternations of clay, sandstone, 
and limestone, following each other in the same order. Thus 
the clays of the Lias are followed by the sands now consid¬ 
ered (see p. 353) as belonging to the same formation, though 
formerly referred to the Inferior Oolite, and these sands again 
by the shelly and coralline limestone called the Great or Bath 
Oolite. So, in the Middle Oolite, the Oxford Clay is followed 
by calcareous grit and coral rag ; lastly, in the Tipper Oolite, 
the Kimmeridge Clay is followed by the Portland Sand and 
limestone (see Fig. 298, p. 322).f The clay beds, however, 
as Sir H. D. de la Beche remarks, can be followed over larger 
areas than the sand or sandstones.J It should also be re¬ 
membered that while the Oolite system becomes arenaceous 
and resembles a coal-field in Yorkshire, it assumes in the Alps 
an almost purely calcareous form, the sands and clays being 
omitted; and even in the intervening tracts it is more com¬ 
plicated and variable than appears in ordinary descriptions. 
* Tableau des Veg. Foss., 1849, p. 105. 
t Conybeare aud Philips’s Outlines, etc., p. 166. 
X Geol. Researches, p. 337. 
