LETTER VI. 
MADREPORE MADREPOREAN POLYPE .FOS&IL MADREPORE 
DIFFICULTY IN ASCERTAINING THE SPECIES TURBINATED 
MADREPORE... ..;VARIETIES OF .REMARKS ON ITS FORMATION. 
w E shall now proceed to the .examination of the genus Madre- 
pore, lunder which genus are placed all those corals, the cavities of 
whiqh»are divided by lamellae disposed in a stellular form. 
The animal which in the recent coral fills these cavities, .was first 
depicted by Donati, in the forty-seventh volume of the Philosophical 
Transactions, Page 105, Plate IV. and in the Natural History of the 
Adriatic Sea, iby the same Author. A correct copy of Honati’s figures 
are here given, since you will thereby -be ibetter enabled to judge of 
the observations I may offer respecting the formation of some of these 
•fossil bodies which are next to be examined. 
The little polypous inhabitant of the madrepore, Plate II. Fig. £5 
3 , . 4 , according -:to the concise jbut perspicuous (description of Donati, 
is composed of 'three different parts; the feet, the shell, and the head. 
The feet are in considerable number, and terminate externally in two 
conical productions, which -being .placed on each side of every one of 
the lamellas which ,give the stellular form to fhe cavity of the coral, 
serve to affix the animal to the circumference ,pf its cell, and may, 
with propriety, be considered as the instruments by which the little 
animal forms the lamellae themselves. The other end of these. conical 
productions unite and form ,round bodies, wfiich possess somewhat of 
the figure and of the properties i of a muscle^; they undoubtedly serving 
to lengthen or shorten the feet, and also most probably to regulate the 
