no 
room xi. fusiform, calcareous bone; the lower part, 
or that imbedded in the sand, is without po¬ 
lypes, which are scattered in various ways over 
the upper half, and the different genera into 
which the family has been divided, depend on 
their disposition. In some, the upper part 
of the coral is furnished with regular branches 
placed on one side of the stem, giving them 
very much the appearance of a feather. In 
the common Sea-Pen ( Pennatula ) the branches 
are again similarly divided, and the tubes 
which have the polypes at their tips are sur¬ 
rounded by a bundle of spicula. In Virgu - 
laria the branches are simple. In Pavonaria 
the polypes are sessile, in a row on each side 
of the front of the stem. In others, as the 
genus Umbellaria , the branches are united to¬ 
gether into a tuft; whilst in the remaining two 
genera the upper part of the coral is fleshy, 
and not branched, the apex of the one, Renellct , 
being expanded into a kidney-shaped disk, with 
the polypes on one of its sides, and the other, 
Veretillum , is club shaped, with the polypes 
scattered over its upper part. 
Cases No. 17 and 18 contain the family of 
Sponges ( Spongiadce ). They resemble the corals 
of the last family in various particulars, but 
their animal nature is not distinctly made out. 
Some naturalists have considered the remains 
of them which we usually have in our collec¬ 
tions. 
