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gelatinous, very contractile coat, on the surface 
of which are studded the groups of tentacula, 
while the body is included in the lamellar 
cells. 
The cells in some of those which form round¬ 
ed masses are compressed and irregularly twist¬ 
ed, and only separated from each other by irre¬ 
gular ridges, as in the Brain Stone ( Meandrina ), 
so called from its resemblance to the convolutions 
of the human brain, when the coral is covered 
with its soft animal. In some allied species the 
cells are small, and the intermediate spaces, in¬ 
stead of being long ridges, form conical emi¬ 
nences, from whence the genus is called Mon- 
ticularia. 
In some, which form foliaceous expansions, 
the upper, and rarely the lower surface of the 
frond is covered with roundish cells, the laminae 
of which are extended over their sides, so as to 
unite the stars one with the other, as in the 
genera Agaricia , Pavonaria , and P olyphyllia. 
The remainder, the corals with aggregate 
stars, are distinguished by each of the stars 
being distinctly circumscribed. 
The cells of many of these are only longi¬ 
tudinally striated on their inner surface, and are 
generally united into a cylindrical, arborescent 
coral. Some of these, as the Madrepores, 
(.Madrepora ,) have the cells prominent and 
closely spread over the whole surface ; in others, 
as 
