Gizzard of the Shell called by Linnzeus Bulla. lignaria. 17 
lar perforation ; which circumftance I mention, as it may poflfibly 
throw fome light on the caufe of the round holes fo frequently met 
with in fhells, particularly among the bivalves; which operation has 
been generally afcribed to fhell-fith of the Purpura kind. It is probable 
that the animal of the abovementioned Bu/a is provided with fome 
organ within the gizzard, for perforating fuch fhells as are too hard 
to be crufhed by the action of the gizzard valves againft each other, 
in order to come at the fifh. The fhells of this bivalve are thick, 
and {hut clofe. The animal was entire; and as it feems impoflible 
for fuch fhells to be broken by any force of fo {mall an’ animal as 
that of the Bulla in queftion, it is poflible that it had begun 
the perforation above mentioned in order to get at the enclofed 
meat. yA 
Since this difcovery was:made, it has been found: that the Bulla 
aperta: of Linnæus, and Bulla patula of Pennant, have. Similar 
gizzards to that of the Bula lignaria; and no doubt all the ipee 
properly belonging to this genus have like parts. | 
It is to be hoped, that thefe obfervations may induce fome able 
anatomift to give fome farther accounts of the animal of the Bulle 
fhells, efpecially as the abovementioned, with other kinds, are found 
living on our own coatts, | 
It only remains for me, Sir, to add a fhort defcription of the 
drawing, Tas. 2. 
No. I. and 2. ‘thew the Bulla lignaria in two views, the back and 
the mouth. 
No. 3. 4 and 5. exhibit the gizzard in three different fites. 
The brown parts between the valves are partly flefhy and 
partly membranaceous, and conneét the valves together: 
a. is the fuppofed entrance into the gizzard: b. the part 
from whence the Mya was taken. | 
Vor. II. D i33 “The 
