9150 Mollusks. 
detect in their slime by making a snail travel over paper tinted by 
lithmus. 
Prof. Buckland to William Baker. 
Oxford, July 24, [1842]. 
You will duly appreciate the bearing of the enclosed [letter of John 
Edward Gray to Professor Buckland, as follows], upon the question 
of holes corroded by garden snails. Please to return it to me. Ifyou 
will gather a snail dry from a tree, and set it crawling on paper coloured 
by lithmus, the purple is instantly turned red; the acid is in small 
quantity, but that is my case. 
John Edward Gray to Prof. Buckland. 
Ilfracombe, July 22, 1842. 
Dear Buckland,—When you read your paper on the holes in the 
limestone, I said there was no reason why the holes might not have 
been made by Mollusca, but that I had never seen holes of the kind 
- so made by them. Since I have been here I have seen several parts 
of the rock in the sea with very irregular holes, and some of them, as 
in your case, communicating with each other or pierced through the 
thickness of the stone. This morning I was so fortunate as to be able 
to determine that they are made by limpets, Patella vulgata. The 
larger holes seem to have been made by large specimens, or those 
that had grown to their full size, and the other cavities which have 
irregularities in their form are pierced by smaller specimens settling 
themselves on the holes after they have been left empty. In some 
holes I found five or six or more young ones, each forming a hole for 
itself on the surface and the cavities of the larger ones. The limestone 
here, or certain parts of it, appears to be very much affected by these 
animals, for it is not uncommon to find a limpet not half an inch long 
having formed a hole more than its height in depth, and the animal, 
I should think, could not be more than a few weeks old. I have 
several specimens, but none small enough to send by post. The holes 
are not so large as those you found. In some places the rocks are 
quite honey-combed with them. They are generally across, or on 
the broad side of the lamine of the strata, but sometimes they are 
made on the edge.—Yours, &c., J. E. Gray. 
William Baker to Prof. Buckland. 
Bridgwater, July 25, 1842. 
Accept my best thanks for the sight of Mr. Gray’s interesting note 
{as above] on the action of the Patella on the rocks near Ilfracombe. 
a 
