198 The Hiftory of ANIMALS. 
but, when living, it makes a much more Angular appearance: all the larger papilla; are 
furnifhed with fpines of a rounded figure, obtufe, and an inch long j on the fmaller 
papilla; ftand fpines of half the length of the others, very flender, and pointed at the 
extremity, and from the holes in the bands the creature throws out a kind of arms, or 
flefiiy filaments, to hold itfelf in it’s place. 
It is a native of the Eaftern Seas, but we have the naked fhell frequent in our cabi¬ 
nets j it is bluifh, when recent, but becomes white in keeping. 
Gentronia deprejfa cordata fpinis capillaceis. 
The deprejfed , cordated Gentronia , with capillaceous fpines . 
This is a large fpecies j it’s figure is oblong and cordated 5 it’s length is three inches; 
it’s breadth at the larger end, where it isfinuatedfo as to give it a cordated form, is two 
inches and a quarter, and it’s depth not more than an inch and half: the aperture 
where the mouth is placed is large, and in the center of the bafe • that for the anus is 
at the extremity of the body, oppofite to the cordated end, not on the fummit, as in the 
rounded fpecies: there run from the center of the upper part of the £hell four rays, 
each formed of a double feries of lines, and each narrow at the bafe, broader in the 
middle, and narrow again at the point: the reft of the furface is covered with fmall, 
roundifh papilla; the colour is whitifh, and, when the creature is alive, there ftand a 
multitude of fhort, flender, and capillaceous fpines on the papilla, and flefhy filaments 
are thruft out from the apertures or perforations at the edges of the lines or rays. 
We have it from the American fhores. 
Gentronia deprejfa plana margine digitato . 
The deprejfed, fiat Gentronia , with a digitated edge . 
This is about two inches in diameter, and is not more than a fixth of an inch in 
thicknefs or height: the fhell is very thin, and of a whitifh colour; it is rounded, 
and in fome part the verge is entire and undivided, but in other parts it is deeply ft- 
nuated or cut in, fo that the parts between the indentings refemble fingers: it has a 
beautiful configuration of four rays on the furface, and has a number of minute papil¬ 
lae, not covering the whole furface, but only difpofed in feries, on which, when the 
creature is living, there ftand very fine, flender fpines. 
We have this on fome of the American fhores: the number of the digitations in 
the fhell is uncertain and irregular; it is ufually from fix, or feven, to twelve. 
Centronia deprejfa plana difco quinquies perforato. 
The deprejfed , plain Centronia , with five perforations on the dijk. 
This is alfoa very Angular fpecies; it is one of thofe which are flatted into the form 
of a thin cake : it’s circumference is round; it’s diameter not lefs than two inches, 
but it’s thicknefs is not more than that of a crown-piece : it’s colour is whitifh, and 
it’s furface furnifhed with a number of papillae in regular feries, and very minute: 
there are four elegant rays formed of perforated double feries of lines running from the 
center toward the verge, in this fpecies j but what is moft Angular is, that there are 
between thefe, toward their extremities, five oblong, oval perforations, a third of an 
inch in length, and half their length in diameter, pierced quite through both furfaces 
of the fhell. 
We have this from the fhores of the American iflands; when perfect, there ftand on 
the papillae a great number of fine, flender, and pointed fpines. 
Centronia deprejfa ad marginem biperforata . 
The deprejfed Centronia , with two perforations near the edge . 
This is another of the flat kinds j it is of a rounded figure, and about an inch and a 
half in diameter: it’s whole thicknefs is not more than that of a crown-piece j it’s 
colour is white, and the edges are undivided ; from the center of the upper furface there 
run five double feries of lines, making fo many fhort, broad, obtufe, and fomewhat 
oval rays $ and toward the edge, on the anterior part of the fhell, there are two oblong 
