500 CLASS ECHINODERMATA. 
the axis, like the pith of a tree, and which are open either at 
the summit, or at the sides, to allow the polypi to pass. 
Their most simple polypi appear principally to resemble the 
hydrz, and the cristatellz. 
TUBIPORA, L., 
Have simple tubes, of a stony substance, each containing a 
polypus. These tubes are parallel, and united together from 
space to space, by transverse laminz, which has caused them 
to be compared to the tubes of an organ. 
The most known species, Tubipora musica, L. Seb. iii. cx. 
89, is of a fine red. Its polypi are green, and have the form 
of the hydre. It abounds in the Indian Archipelago. 
It would seem, that it is to the tubipora that we should ap- 
proximate some fossil polyparia, likewise composed of simple 
tubes, such as the CATENIPORA, Lam., in which the tubes 
are arranged upon lines, intercepting empty meshes; Twbi- 
pora catenulata, Gm. ‘The FavositsEs, id. (Corallium 
Gothlandicum) composed of hexagonal tubes, crowded closely 
together, &c. 
TUBULARIA, L., 
Have simple or branched tubes, of a corneous substance, from 
the extremities of which the polypi issue forth, and show 
themselves. 
The polypi of the fresh-water tubularie,—PLUMATELLA, 
Bosc. appear very much akin to the crystatelle, in the dispo- 
sition of their tentacula. 
We have some which creep over the plants of our dormant 
waters. (Tubularia campanulata, Res.) 
TUBULARIA MARINA, 
Have polypiwith two ranges of tentacula; the exterior one 
being developed in radii, the interior raised in the style of a 
tuft. 
