NATURAL HISTORY 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 marble 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 

 Pentacrinus caput Medusce, an inhabitant of the genial 

 waters of the Caribbean Sea. 



The chief species of the Crinoideans found in the 

 Silurian strata are: Encrinus liliformis, Dimencrinites 

 decadactylua, Cyathocrinites gonodactylus, Hypantho- 

 crinites decorus, and Cupressocrinus ci-assits. 



The advent of coralline animals also belongs to the 

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

 shall speak hereafter. A hue of reference must be given 

 to the genus Euomphalus, 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 



a, I'entacrinites Brinrens, reduced ; 6. the same from the Lias of 

 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- 

 fied under a genus named Sphagodus, or murderous 



tooth ; they were, undoubtedly, the pirates 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 PERIOD. 

 Rocks. Fossils. 



Hard sandstone, slates, and conglo 



merate beds, 

 Calcareous sandstone, coarse grits, 



and purple shales, 



Limestone and shale; 



" f Crinoideans and Corals. 

 Brachiopods. 



tolites. 



Shale, with calcareous limestone, . Marine molluscs. 

 Argillaceous limestone, .... Crinoideans. 

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

 Sphayodus genus. 



;one, and mud-) 



THE DEVONIAN PERIOD. 



We now come to an investigation of the natural his- 

 tory of the Devonian, or Old Red 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 Encrinites 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 different from any of 

 the species which inhabit our present seas. 

 Many 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 with 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 Coccosteus, 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 Pter- 

 iclitJiys, or Winged Fish, whose fossil remains 

 were first discovered by Hugh 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 r 

 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- 



