niGH STANDING OF THE PLACOIDS. 123 



IJIGH STANDING OF THE PLACOTDa 

 OBJECTIONS CONSIDERED. 



We have seen that some of the Silurian placoids were large 

 of size : the question still remains, " Were they high in in- 

 telligence and organization 1 



The Edinburgh Reviewer, in contending with the author 

 of the " Vestiges," replies in the afl5.rmative, by claiming for 

 them the first place among fishes. " Taking into account," 

 he says, " the brain and the whole nervous, circulating, and 

 generative systems, they stand at the highest point of a na- 

 tural ascending scale." They are fishes, he again remarks, 

 that rank among " the very highest types of their class." 



" The fishes of this early age, and of all other ages pre- 

 vious to the Chalk," says his antagonist, in reply, " are, for 

 the most part, cartilaginous. The cartilaginous fishes — 

 the Chondropterygii of Cuvier — are placed by that naturalist 

 as a second series in his descending scale ; being, however, he 

 says, * in some measure parallel to the first.^ How far this 

 is dijSerent from their being the highest types of the fish class, 

 need not be largely insisted upon. Linnaeus, again, was so 

 impressed by the low characters of many of this order, that 

 he actually ranked them with worms. Some of the cartila- 

 ginous fishes, nevertheless, have certain peculiar features of 

 organization, chiefly connected with reproduction, in which 



