NATURAL HISTOEV OF THE PRIMEVAL WORLD. 



the column and ossicula are often filled with white 

 calcareous spar, while the ground of the marble is of a 

 dark reddish-brown colour." 



Thus, then, the raarble which now adorns our habi- 

 tations was elaborated, ages ago, by countless myriads 

 of ocean's living flowers — those rare and beautiful 

 organisms whose principal living representative is the 

 Pentacriims caput Medusce, an inhabitant of the genial 

 waters of the Caribbean Sea. 



The chief species of the Crinoidoans found in the 

 Silurian strata are: — Encriinis lillformis, Dimencrimtes 

 decndactybin, Cyalhocrinites (jonodiwtylus, Hijpanlho- 

 crjnites decorus, and Cupressocriiius crassus. 



Tlie advent of coralline animals also belongs to the 

 period we are now considering. Of these, however, we 

 shall speak hereafter. A line of reference must be given 

 to the genus Ettomphulus, so named in allusion to the 

 deeply umbilicated, or navel- like, depression of its disc. 

 The animal inhabited an univalve shell, divided inter- 

 nally into several chambers. As it grew in size, it 



Radi- 

 Gi'iip- 



(I, PentacrinltcB Briarens, reduced; I, the same from the Lias ot 

 Lyme Kegis, natural size. 



abandoned the innermost chamber, which served it for 

 an asylum, leaving it vacant, and secreting behind itself 

 a partition wall. This operation was repeated at each 

 successive stage of its growth, so that the animal and 

 its house expanded simultaneously. 



The fishes belonging to this period have been classi- 

 (ied under a genus named Sphagodus, or murderous 



tooth ; they were, undoubtedly, the piiates of the 

 Silurian seas, whose ravages confined within reasonable 

 limits the increase of the lower organisms. 



We tabulate, as before, the rocks and fossils of the 



UPPEK SILURIAN PERIOI). 



Roclcs. Fossils. 



Hard sandstone, slates, and conglo-) „ • •, , ^ , 



meratebeds, .... J" Cnno.deans and Corals. 



Calcmeous sandstone, coarse grits, ) „ ^ • 

 and purple shales, . . . . .) Brachiopods. 



Limestone and shales, felspathici ,, . ,, 



sandstone, grit, argillaceous shales, { *'";"" ."°""''== ' 

 and concretionary and thick-bedded f . ," ' liiiobites; 

 limestone, ) '"'"^'^• 



Sliale, with calcareous limestone, . Marine molluscs. 



Argillaceous limestone, .... Crinuideans. 



Micaceous grey sandstone, and mud- 1 Crustaceans; Fish of the 

 stone, / Sphayodus genus. 



T1II3 DEVONIAN PEUIOD. 



We now come to an investigation of the natural his- 

 tory of the Devonian, or Old lied Sandstone, so called 

 because the formation is very largely developed 

 in the county of Devon. 



The seas were still of vast extent, but their 

 surface was diversified by scattered islets, on 

 whose rocky shores the Mollusca and Articulata 

 of the period passed through their various stages 

 of existence. Here the lily-like Eiicrinites still 

 bloomed and flourished ; on the sandy shore bur- 

 rowed enormous annelids, large as a man's arm ; 

 the eurypterus still paddled through the teeming 

 waters ; and throngs of strange ganoid fishes 

 fluttered to and fro, in quest of food or in flight 

 from an enemy. 



The fishes were, perhaps, the most conspicuous 

 members of the Devonian fauna. Uncouth were 

 they of form, and widely diti'erent from any of 

 the species which inhabit our present seas. 

 l\Liny were shut up in a complete armour of 

 bony plates ; others glittered with strange coats 

 of hard enamelled scale ; not a few were fur- 

 nished v/itb fin-spines and other external wea- 

 pons of attack and defence. So curious and 

 unusual was their conformation that early obser- 

 vers not unfrequently set them down as crusta- 

 ceans, reptiles, or even "huge water-beetles." 



Take, for example, the Coccosietis, which may 

 be described as a half-armoured or partially 

 plated individual, only the upper part of the body 

 down to the fins being protected by scales. It 

 derives its scientific name ("berry-bone") from 

 the small berry-like projections or tubercles which 

 studded its plated surfaces. 



Still more remarkable in aspect was the Pler- 



ichthys, or Winged Fish, whose fossil remains 



were first discovered by Ilugh Miller. His 



description of this apparently monstrous anomaly, 



which nevertheless was admirably fitted to discharge 



its peculiar functions in the economy of creation, will 



interest the reader. Imagine, he says, the figure of a 



man roughly drawn in black on a grey ground, the 



head amputated at the shoulders, the arms extended 



as in the attitude of swimming, the body rather long 



than otherwise, and narrowing from the chest down- 



