358 
ELEMENTS OF GEOLOGY. 
Pentacrinus in the Lias; and the latter genus is found in 
nearly all the formations from the Lias to the London Clay 
inclusive. It is represented in the present seas by the deli¬ 
cate and rare Pentacrinus caput-medusce of the Antilles, 
which, with Comatula, is one of the few surviving members 
of the ancient family of the Crinoids, represented by so many 
extinct genera in the older formations. 
Fishes of the Lias.—The fossil fish, of which there are no 
less than 117 species known as British, resemble generically 
those of the Oolite, but differ, according to M. Agassiz, from 
those of the Cretaceous period. Among them is a species of 
Lepidotus (i. gigas^ Agass.), Fig. 375, which is found in the 
a Fig. 375. 
Scales of Lepidotus gigas, Agass. 
a. Two of the scales detached. 
Lias of England, France, and Germany.* This genus was 
before mentioned (p. 316) as occurring in the Wealden, and 
is supposed to have frequented both rivers and sea-coasts. 
Another genus of Ganoids (or fish with hard, shining, and 
Fig. 376. 
h. Scales of jLchmodus a. JEchmodus. Restored outline. c. Scales of Dapedius 
LeacML monilifer. 
enamelled scales), called ^chmodus (Fig. 376), is almost ex¬ 
clusively Liassic. The teeth of a species of Acrodus^ also, 
are very abundant in the Lias (Fig. 377). 
* Agassiz, Poissons Fossiles, vol. ii., tab. 28, 29. 
