ON ECHINODERMATA. 539 
and very slowly. When they swim, they are seen to present 
their body obliquely to the action of the water, and to agitate 
their radii slightly. When they want to descend, they sus- 
pend all motion, and allow themselves to fall perpendicularly 
to the bottom. When they have succeeded in getting a shell, 
they suck out the animal from it through the aperture. They 
possess a wonderful power of reproduction. 
The text is sufficiently explanatory of the organic differ- 
ences which distinguish the genera. 
ENCRINUS was a name first proposed by Ellis, to desig- 
nate a very singular animal, whose place is still uncertain 
enough in the natural series, so much so that while many 
naturalists, with Guettard and Ellis, place it with the family 
of asteriz, others with Linnzus, range it with the polyparia, 
near the Isis. Ellis, in 1761, read to the Royal Society, a 
very interesting memoir on this same genus, having made his 
observations on an individual which came from the coast of 
Barbadoes. This genus does not appear even yet to have 
been examined with all the attention it deserves, for it seems 
indubitable that some of its species, no longer in our present 
seas, must have been very common there anciently, since 
nothing is more multiplied in certain calcareous strata, than 
these fossil remains, known under the names of entrochi, en- 
crinites, &c. Our limits will not permit us to enlarge on the 
characters of this genus, for which we must refer to the text 
of Cuvier. 
These animals, very probably, live in the bottom of the 
sea, at considerable depths ; but it is not even known whether 
they are fixed there, which, however, appears very likely to 
be the case. It is to chance alone that the discovery has been 
owing of three or four individuals only, which exist in the 
European collections, and which come from the American 
seas. 
Under the denomination of ECHINUS, Linnezus, and the 
