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THE GEOLOGIST. 
e 
Fig. 3. — Diagram of restored Pteraspis. 
of the shield. Professor Huxley informs me that he believes them to 
be the sites (if I may so say) of mucous follicles. I have thouoht this 
worth mentioning in a note, as they have never before been noticed. 
When and how was the Isle of Wight severed from the Mainland ? , 
SiE, — On two diflerent occasions inquiries have been made in the pages 
of the ' Geologist,' as to the period at which the Isle of Wight was torn 
from the mainland and entrusted to the rude guardianship of the ocean. 
The subject is an interesting one, especially in its geological aspects ; and 
as I have given some attention to it, I will attempt to reply to the in- 
quiries of your Lymington correspondent. 
I am not aware that there is the least particle of historical evidence that 
gives countenance to the famous passage in Diodorus Siculus that has 
been interpreted by various writers as proving that, when he lived, the 
channel of the Solent was fordable at low water. As the particular island 
of which Diodorus is speaking, was one from which the miners of Cornwall 
were in the habit of exporting their minerals, and there is a -Bmall isle (St. 
