6 
NATURAL HISTORY OF SELBORNE. 
LETTER III. To T. PENNANT. Esa. 
The fossil-shells of this district, and sorts of stone, such as have 
fallen within my observation, must not be passed over in silence. 
And first T must mention, as a great curiosity, a specimen that 
was plowed up in the chalky fields, near the side of the Down, 
and given to me for the singularity of its appearance, which, to 
an incurious 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 Linnsean genus of mytilus, and the species of 
crista galli; called by Lister, restellum j by Rumphius, ostream 
plicatum minus; by D'Argenville, auris porci, s. crista galli j and 
by those who make collections cock'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 preservation. 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 sutures 
the one into the other, the alternate flutings or grooves, and the 
curved form of my specimen, being much easier expressed by the 
pencil than by words, I have caused it to be drawn and engraved.* 
* Ostrea carinatat or keeled oyster of Lamark. The author is however mistaken in the sup- 
position that this identical species is yet in being, it having long since been satisfactorily shown 
that no species of organism, the remains of which are imbedded in the old limestone formations, 
exists at the present time; although many recent species (or those which are now living) are very 
closely allied to some — even of the most ancient — of those which are exclusively fossil. No 
species whatever is common to even the secondary and tertiary formations (as they are termed). 
