320 



FOSSILS OF THE LIAS. 



I'Ch. XXI 



Fig. 40S. 



/^. y# Xf^ A^;-. v^^^ <» . 



Fig. 409. 



m 



Extracrinua Brinreus. ^ nat. size. 

 (Body, arms, and part of stem.) 

 Lias, Lyme Kegis. 



Opliioderma Egertoni, E. Forbes. 

 Lias Marlstone, Lyme Eegis. 



The Extracrinus Briar eus (removed by Major Austin from Pentacri- 

 nus on accoimt of generic differences) occurs in tangled masses, forming 

 thin beds of considerable extent, in the Lias of Dorset, Gloucestershire, 

 and Yorkshire. The remains are often highly charged with pyrites. 

 This Criuoid, with its innumerable tentacular arms, appears to have been 

 frequently attached to the drift-wood of the liassic sea, in the same man- 

 ner as Barnacles float about at the present day. There is another species 

 of JExtracrinus and several of Pentacrlnus 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 delicate and 

 rare Pentacrlnus Capui-medusoB of the x\ntiHes ; and this indeed is 

 perhaps the only surviving member of the great and ancient family of 

 the Crinoids, so widely represented throughout the older formations by 

 the genera Taxocrinus^ Actinocrinus, Cyatliocrinus^ Encrinus, Apiocri- 

 nus, and many others. 



The fossil fish re- « ^^s- ^lo. 



semble genetically 

 those of the oolite, 

 belonging all, ac- 

 cording to M. Agas- 

 siz, to extinct gen- 

 era, and di tie ring 

 for the iiiost part 

 from the i('hthyolites 

 of the Cretaceous pe- 



Scales of Lepidotus gigas. Agas. 

 a. Two of tlie scales detached. 



