OF SELBORNE. 21 
LETTER IIl. 
Tue 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, I 
must mention, as a great curiosity, a specimen that 
was ploughed 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 re- 
ality, a bivalve of the Linnean genus of mytilis, 
and the species of crista galli: called by Lister 
rastellum ; by Rumphius, ostreum plicatum minus ; 
by D’Argenville, auris, porci, crista galli; 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, permis- 
sion 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 bi- 
valve is only known to inhabit the Indian Ocean, 
where it fixes itself to a zoophyte known by the 
name gorgonia. 
Cornua ammonis are very common about this vil- 
lage. As we were cutting an inclining path up the 
Hanger, the labourers found them frequently on 
that steep, just under the soil, in the chalk, and of 
a considerable size. In the lane above Well-head. 
in the way to Emshot, they abound in the bank, in 
