53 



MoUusca, Corals, and the remains of genera of inshore dwelHng^ 

 fish indicate a shallower marine deposit. The greater part of the 

 American Devonian, on tlie contrary, was apparently laid down in 

 an open sea, and thus a monster marine fauna flourished, not so 

 generally rejiresented in Europe, but it is interesting to note the 

 identity of a few species occuring in localities where the beds are 

 of similar structure to those of contemporaneous age in Europe. 

 In both worlds the formation is ahke distinguished by the great 

 preponderance of ganoid over elasmobranchiate fishes. 



The condition existing during the formation of the Devonian 

 rocks are well illustrated at the present day by the fresh-water 

 lakes, mighty rivers, and extended coast line of the African and 

 American continents, and it is a most suggestive and significant 

 fact that the genera of li'V'ing ganoid and dipnoid fishes most re- 

 sembling the palfeozoic forms are now, with two exceptions, found 

 on those continents alone. Taking the various orders of Professor 

 Huxley's comprehensive classification in succession, we find that no 

 traces of the first or lowest order, the FJumjrigoliranchii, which 

 contains only the " gullet breathing" lancelet have been found in 

 a fossil state. Tins is easily accounted for, hoAvever, by the soft 

 and perishable structure of the species, of wliich no remains could 

 possibly be preserved in the finest sedimentary strata, and, there- 

 fore, the non-representation of this lowest form of ichthyic life in 

 " the records of the rocks " becomes less remarkable. 



Of the cartilaginous Mars'qwhranclm, comprising the hag fishes 

 and lampreys, the horny teeth alone would be susceptible of 

 preservation, and their absence has been commented on as 

 negativing the evidence of progressive development among fishes, 

 as it is obvious the most simply constracted forms should appear 

 first on the scene of life in order to give place to their more highly 

 organised descendants. 



In 1856, Pander, in his magnificent work on the Silurian and 

 Devonian fishes of the Eussian Baltic Provinces, gave numerous 

 figures of what he supposed to be the teeth of small sharks, from 



