19 
grinding of their singularly formed jaws. The Saxieav* 
Bugosa lias its projectile organ or tongue, a rough rasp- 
like structure which may he supposed by repeated 
application to be capable of wearing down the substance 
of the rock; but in other boring animals, some of which 
are naked, and perform the operation on the shells of 
Bivalves, for the purpose of devouring the Molluslt within, 
no such structure has hitherto been detected ; and the 
Saxicaya Rugosa itself seems indisposed or incapable to 
penetrate any other rock beside that ol limestone, [t 
is probable 'therefore, that some digestive application 
with chemical powers is first made use of, by which the 
mechanical operation of the tongue is the more easily 
secured. This slender organ is sometimes found protru- 
ded, occasioually in a tortuous direction, in a passage 
through the stone, to the length of nearly two inches, with 
a transverse measurement not exceeding its own breadth : 
a circumstance which seems to show, that the operation is 
as much for obtaining food, as for the purpose of enlarging 
its habitation. 
. This species of Saxicava preserves its membranous covcr- 
In g while enclosed in its rocky cave ; but when, as is 
s °inelimes the case, it has become enveloped in a mass of 
c ° r al, it becomes denuded, and so changed in form as 
s °arcely to be recognized. 
VENERIRUPIS. 
GENERIC CHARACTER : The shell transverse, sides 
unequal; the posterior side very short, the anterior gaping 
slightly. Hinge with two teeth in the right valve, and 
three in the left, sometimes three in each, the teeth small, 
upproximate, parallel, and but little or not at all divergent. 
t Ligament external. 
' V. DECUSSATA. Venus Literata. Tuft. Lin. Pen. 
Brit. Zo., vol. 4, pi. 57, fig. 53. V. Decussata. Mont. 
Test. Brit., vol. 1, p. T24. " Stew. Elem,, vol. 2, p. 382. 
Tenerupis D. Flem. Brit. An., p. 451. Common in 
harbours through which a fresh stream flows. I have 
obtained it from Looe, so near the surface of the ground, 
H'at the muscles had fastened their byssus to it. This 
a ud the following are termed hens, to distinguish them 
« Jf°m cocks or cockles. 
V - PULLASTRA. Venus P. Mont. Test. Brit., vol. 1, 
P* 125. Venerupis P. Flem. Brit. An., p. 451. This 
I s by Sowerby consituted the type of the genus Pullastra. 
R is common, though by several Naturalists strangely 
overlooked or confounded with less common kinds. It 
burrows, in rather firm ground, a few inches beneath the 
s urface. 
