Ch. XXL] 



FOSSILS OF THE LIAS. 



321 



riod. Among them is a species of Lepidotus [L, gigas, Agas.), fig. 410, 

 wliicli is found in the has of England, France, and Germany.* This 

 genus was before mentioned (p. 262) as occurring in the Wealden, and 

 is supposed to have frequt^nted both livers and coasts. Another genus 

 of Ganoids (or fish with hard, shining, and enamelled scales), called 

 JEchmodus (see fig. 411), is almost exclusively Liassic. The teeth of a 

 species oi Acrodus^ also, are very abundant in the lias (fig. 412). 



Fig. 411. 



Scales of ^chtnodus 

 Leachii. 



a. ^chmodus Eestored outline. 



Fig. 412. 



c. Scales of Dape- 

 dius monilifer. 



Acrodus nohilis, Aaras. (tooth) ; commonly called fossil leach. 

 Lias, Lyme Eegis and Germany. 



But the remains of fish which have excited more attention than any 

 others, are those large bony spines called ichthyodorulites (a, fig. 413), 

 which were once supposed by some naturalists to be jaws, and by others 



Fig. 413. 7, 



Hylod.m reiiculatm, Agas. Lias, Lyme Eegis. 



a. Part of fin, commonly called Ichthyodorulite. 

 o. Tooth. 



weapons, resembling those of the hving Balistes and Silurm ; but which 

 M. Agassiz has shown to be neither the one nor the other. The spines, 

 in the genera last mentioned, articulate with the backbone, whereas there 

 are no signs of any such articulation in the ichthyodorulites. These last 



* Agassiz, Pois. Fos. vol ii. tab. 28, 29. 

 21 



