420 



FOSSILS OF THE LIAS. 



[Ch. XXL 



arms, appears to have been frequently attached to the driftwood of 

 the liassic sea, in the same manner as Barnacles float about at the 



Fig. 449. 



Fig. 450. 



Mctracrinus Briareus = Pentacrinus 



Briareus. ■§- nat. size. 



(Body, arms, and part of stem.) 



Lias, Lyme Eegis. 



Ophioderma Eg&rtoni, E. Forbes. 

 Middle Lias, Seatown, Dorset. 



present day. There is another species of PJxtracrinus and several of 

 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 repre- 

 sented in the present seas by the delicate and rare Pentacrinus Caput- 

 medusce of the Antilles, which, with Comatula, are the only surviving 

 members of the great and ancient family of the Crinoids, so widely 

 represented throughout the older formations by the genera Taxocrinus, 

 Actinocrinus, Cyathocrinus, JUncrinus, Apiocrinus, and many others. 



Fig. 451. 



Scales of lepidohos gigas, Agass. 

 a. Two of the scales, detached. 



The fossil fish resemble generically those of the oolite, belonging 

 all, according to M. Agassiz, to extinct genera, and differing for the 

 most part from the ichthyolites of the Cretaceous period. Among 



