18 MR. GeorGEe Humpurey’s Account, &c, —— 
"The three valves which compofe the gizzard, the leaft of which 
is placed between the other two, as exprefíed at No. xare ofa 
nature between. fhell and bone: the two larger, which are fimi- 
lar, are nearly flat. The furface of the outfide, No. 6. is {mooth, 
except à large depreflion in the middle, and;glofly.. The: middle 
of the infide, No. 7. rifes in: proportion as the other:is depreffed, 
and is rough, as if intended for maftication, which its promi- 
nency allo favours, and it alfo appears to» be hardeft there. A. 
yellow griftly fubftance furrounds this part, with which it is pro- 
bable the valves are moved; from whence it 1$ finely ftriated to the 
edge, which is a little fharp. 
No. 8. The leaft valve appears like one of the others bent out- 
wards, but fo that the two edges do not meet, particularly at the 
two ends, where they are a little diftant, forming a groove wideft 
at the extremities, as feen at No. 4 The infide is rough at the 
centre, and has the circular griftle-like part that is in each of the 
other valves. 
Other particulars are fo well exprefled in the drawing, as to need 
no elucidation. 
It may not be amifs to remark, that the Bu//a is deftitute of an 
operculum ; and there is certainly. no occaf ion for one, as the far 
greater part of the animal is on the outfide of the.fhell, and can- 
not, on account of its gizzard, contract itfelf fo as to retire within 
it: but as it refides in deep water, it is perhaps as fafe there 
from fifh, crabs, and other depredators, as thofe are who live 
nearer the fhore, and barricado the mouths of their fhells with 
their opercula. 
: I am, Sir, 
Your obliged and moft humble fervant, 
i GEORGE HUMPHREY. 
Albion-ftreet, Surry end of Black- 
Fryar’s Bridge, 1ft Dec. 1789. 
