8 
NATURAL HISTOEY 
LETTER III. 
TO THOMAS PENNANT, ESQUIRE. 
HE fossil shells of this district, and sorts of 
stone, such as have fallen within my obser- 
vation, must not be passed over in silence. 
And first I must mention, as a great curi- 
osity, a specimen that was ploughed up in 
the chalky fields, near the side of the Down, and given to 
mo for the singularity of its appearance, which, to an in- 
curious eye, seems like a petrified fish of about four inches 
long, the cardo passing for a head and mouth. It is in 
reality a bivalve of the Linnaean genus of Mytilus and the 
species of Crista galli; called by Lister, Rastellum ; by 
Eumphius, Ostreum plicatum minus ; by D^Argenville, Auris 
porci, s. Crista galli; and by those who make collections, 
cocJc^s comb. Though I applied to several such in London, 
I never could meet with an entire specimen; nor could 
I ever find in books any engraving from a perfect one. 
In the superb museum at Leicester House,^ permission 
was given me to examine for this article ; and though I was 
disappointed as to the fossil, I was highly gratified with the 
sight of several of the shells themselves in high preserva- 
tion. This bivalve is only known to inhabit the Indian 
ocean, where it fixes itself to a zoophyte, known by the 
name Gorgonia. The curious foldings of the suture the 
^ This was originally the property of Sir Ashton Lever, and long 
known as the Leverian Museum. Pennant characterized it as " the 
most astonishing collection of the subjects of natural history ever col- 
lected, in so short a space, by any individual." The specimens of 
natural history and of art, which it contained, were exhibited for many 
years, but were finally disposed of by auction, in 1806. Some idea may 
be formed of the extent of the collection at that time by the duration 
of the sale, which lasted for sixty-five days, and by the number of the 
lots, which amounted to 7879. — Ed. 
