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212 Agassiz’s Contributions to the 
in the facts ascertained by Miller, is the extraordinary similarity of so 
many larve, of such different orders and different families as the Ophiu- 
cal peculiarities. It is next very remarkable, that the more advanced 
larval state of Echinoids ar 
at similarity, that a young Amphideius hardly differs from a young 
Bchinus, Finally, not to extend these remarks too far, I would only add, 
rather a general resemblance to Cidaris, on account of their large spines, 
than to Echinus proper. Now, these facts agree exactly wit what is 
Clypeastroids is known, it will, no doubt, afford other links to connect a 
ger number of the members of the series.” 
The young Ganoid of our lakes and rivers has the prolonged 
caudal vertebral column of the ancient Ganoid; and all the an- 
cient fishes have cartilaginous internal skeletons instead of bony, 
resent peculiarities of structure which are now known as en 
i growth of existing 
pecies; Professor Owen alludes to facts of this kind on page 192 
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