



J^ sS\ 



J^cH. 



67 



tlie Devonian seas became extinct before the mountain limestone deposits began to 

 accumulate, so that, with one or two exceptions at most, each system of ancient rocks 

 has its own peculiar species of Crinoids, none of which occur in deposits newer than the 

 group in which it first appeared. 



Sir Roderick Murchison, at page 20G of his work on Russia and the Ural Mountains, 

 makes the following observation relative to the occurrence of one species of Cyathocrinus 

 in the Permian strata. 



"The Crinoidea are extremely scarce, and of seventy to seventy five species which 

 inliabited the carboniferous seas, one only, the Cyathocrinus j)lanus (Miller) lived during 

 tlie Permian epoch. Even this solitary species is extremely rare and we are as yet 

 unacquainted with it in Russia." 



Sir Roderick does not state the evidence on which the opinion as to the Cyalhocrinus 

 planus occurring in the Permian system is founded. It is true that Prof. Sedgwick in 

 the transactions of the Geological Society, vol. 3, second series, page 126, states that 

 portions of columns of two species of Crinoidea are found in great abundance in the 

 quarries of Magnesian limestone near Humbleton; and also that specimens from Hum- 

 bleton andTynemouth had been examined by Mr. Miller, and were referred by liim to 

 the C. Planus. 



It is almost needless to repeat that, considerable difficulty and doubt must of necessity 

 prevail in referring portions of columns to particular species unless the structure of the 

 whole column from its base to the apex is well known, or the particular portion descri- 

 bed as belonging to an ascertained species has been seen attached to the Crinoid to which 

 it is referred. It is therefore far from certain that the C Planus lived during the 

 Permian epoch. 



