! The Hijlory ^ANIMALS, 177 
ter only clay or mud when the creature got into it, but to have petrified and become 
done afterwards: the Ludus Helmontii, which is the refidence of thefe fifh on our 
own coafts, oftener than any other fpecies of done. Teemed to favour this opinion, as 
many have erroneoiifly fuppofed that done to be petrified clay, before they were in¬ 
formed of this additional appearance in favour of the eonjedure: but the harded 
dones are found pierced by them in other places; and, about the coafts of Italy, pieces 
of wrought marble are frequently taken up after wrecks, which, if they have lain only 
a few years in the fea, are ufually fpoiled by the holes made in them by thefe creatures. 
We had lately a fpecimen of a very hard done prefented to the Royal Society here, in 
which were living fhell-fifh ; thefe were determined to be Pholades, but they were, 
in reality, one of the mytulus kind, defcribed already in it’s place : the general opinion 
was, that the done had grown about thefe creatures; nor was it without difficulty that 
I perfuaded that learned body, that the creatures had a power of making their way 
into hard fubftances, while hard, by producing fome pieces of oak, in which there were 
feveral of them lodged. 
Pholas albefcens valvis majoribus brevibus , fubovatis . 
The white Pholas, with the larger valves Jhort and fuboval. 
This fpecies is lingular, on account of s the fmallnefs of the fhell in proportion to 
the body of the animal: in mod of the Pholades, the fhell is not large enough to 
furround and compleatly inclofe the creature, the deny lides of the cavity it is lodged in 
anfwering that purpofe in it’s place; but, in this particular kind, the larger valves bear 
no proportion to the bulk of the body : they are of a whitifh colour, of a fuboval fi¬ 
gure, fomewhat hollowed, and longitudinally driated; their furface is rough, and their 
texture tender and delicate; the two fmaller valves are placed at the back of the 
others, in a contrary direction ; and the fifth or lad valve is long, llender, and convex, 
and covers the whole hinge : thefe three have a radiated furface, but they are fmoothet 
than the others. 
This fpecies is frequent on our Kentilh and Sufiex coafis; I have met with it in 
great abundance about Shepey ifland, and among the Bognor rocks in Sulfex. 
Pholas fubrubens prof unde fulcatus et afper. 
The reddijh, deeply furrowed and rough Pholas. 
This is four inches long, and about two in diameter: the two principal valves are 
oblong, larged near the middle, and deeply hollowed ; they are very thin and delicate; 
their colour is a pale but elegant red, often variegated with white, and their furface is 
deeply furrowed with parallel, longitudinal, and not very diftant lines; the fpaces be¬ 
tween rife up into ridges, and their furface is rough; the other three valves are final!, 
and are placed at the back of thefe; two are oval, and one is oblong and very flender. 
This fpecies is found in ftones about the American coafts, and not unfrequently 
makes it way into the larger corals, and other dony plants, and into feveral other fo¬ 
lk! fubdances. 
. \ 
Pholas angujlior tenuijfmus et afper. %\)t jffllllfett 
The narrow , thin , and rough Pholas. 
This is the larged known fpecies of Pholas: it is fix or feven inches long, and, with 
that length, not more than two inches in diameter : the two large or principal valves, 
which are all that we ufually meet with, are of a very tender and delicate dructure, 
and are hollowed, and of a beautiful white : they are frnooth on the inner furface, but 
on the outer they are deeply furrowed, both in a longitudinal and tranfverfe diredion, 
and are rough to the touch in the manner of a file: the three other valves are, as in 
the former fpecies, two fhort and rounded at the extremities, and the other very long, 
very narrow, and hollowed ; this runs along the back, covering the whole hinge. 
This fpecies is brought to us from the American coads; it lives in hard dones, but 
is feldom met with, except loofe on the fhores, when it has been diflodged by fome 
accident, as the breaking of the body that inclofed it: for this reafon a fingle valve is 
all that is ufually found, and often that not entire. 
Z z 
The 
