391 



These specimens show the obscurely stratified quartzose rock, 

 with great numbers of small grains and pebbles firmly cemented 

 to its surface ; and it would seem that the whole rock was formed 

 by the gradual solidification of particles thus cemented together, 

 the solid rock encrusted with the deposits of the marine animals 

 above-mentioned, many of their tubes being preserved, and their 

 orifices opening in all directions ; there are, also, several speci- 

 mens, which, from their lightness, seem to contain little or no 

 sandy or quartzose material, being almost entirely made up of the 

 exuvise and calcareous excretions ofserpul0e,balani and nullipores, 

 whose tubes and tortuous excavations are everywhere seen ^ 

 when fresh, some of the colors were of a beautiful sea-green, 

 and red ; and the latter color is, even now, very distinct in some 

 portions ; some of the excavations in the reef were lined with 

 coriaceous growths and tubes, some of which are preserved in 

 the dry state, giving to the sides the feel of the thickest and 

 softest velvet ; in these excavations, which were of a foot or two 

 in depth, numerous small fishes of most brilliant colors were 

 darting about, which Mr. W. O. Ayres determined to be princi- 

 pally young choetodons. 



Dr. Darwin says that no true coral enters into the composition 

 of this reef; but Dr. Kneeland exhibited two specimens which he 

 had obtained there, much resembling Meandrina cerebriformis. 



It seems altogether the most probable that this reef has been 

 elevated after its consolidation, according to the first supposition 

 of Dr. Darwin ; such processes, we know, are constantly going 

 on, and particularly on the eastern coast of the American con- 

 tinent. This reef is a striking instance of the advantages result- 

 ing to man from the myriads of marine architects ; and he 

 thought these specimens would be interesting, as showing some 

 of the steps in the process of erection and preservation. There 

 is reason to believe that this reef has no necessary connection 

 with coral formations ; but is probably fringed with coral at its 

 base towards the sea, from which source may have come the 

 specimens of Meandrina exhibited. 



Dr. Kneeland read extracts from a communication from Dr. 

 Gorrie, of Appalachicola, on the change of level between the 



