2IO THE HTSTOEY OF CREATION. 



teeth and fin-spikes. These are found in the older 

 formations in such quantities, varieties, and sizes, that we 

 may, with certainty, infer a very considerable develop- 

 ment of Primaeval fish in those remote ages. They are even 

 found in the Silurian strata, which contain but few 

 remains of other Vertebrata, such as Enamelled fish (and 

 these only in the most recent part, that is, in the upper 

 Silurian). By far the most important and intei'esting of 

 the three orders of Primseval fish are Sharks ; of all still 

 living double-nostriled animals, they are probably most 

 closely allied to the original primary form of the whole 

 group, namely, to the Proselachii. Out of these Proselachii, 

 which probably differed but little from genuine Sharks, 

 Enamelled fish, and the present Primaeval fish, in all prob- 

 ability, developed in one direction, and the Dipneusta, 

 Sea-dragons, and Amphibia in another. 



The Ganoid, or EnaTiielled fish (Ganoides), in regard to 

 their anatomy stand midway between the Primaeval and the 

 Osseous fish. In many characteristics they agree with the 

 former, and in many others with the latter. Hence, we infer 

 that genealogically they form the transition from Primaeval 

 to Osseous fish. The Ganoids are for the most part extinct, 

 and more nearly so than the Primaeval fish, whereas they 

 were developed in great force during the entire palaeolithic 

 and mesolithic periods. Ganoid fish are divided into 

 three legions according to the form of their external 

 covering, namely, Mailed, Angular-scaled, and Round- 

 scaled. The Mailed Ganoid fish (Tabuliferi) are the oldest, 

 and are directly allied to the Selachii, out of which they 

 originated. Fossil remains of them, though rare, are found 

 even in the upper Silurian (Pteraspis ludensis of the 



