8 THE NATURAL HISTORY 



LETTER III 



TO THOMAS PENNANT, ESQUIRE 



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 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 an 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 Rumphius, 

 Ostreum plicatum minus ; by D'ArgenviUe, Auris Porci, s. 

 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, 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 suture 

 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. 



Comua Ammonis are very common about this village. 

 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 a darkish sort of marl ; and are usually 

 very small and soft: but in Clay's Pond, a little farther 



