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THE GEOLOGIST. 



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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 difi'erent 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 Avill 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 wliich Diodorus is speaking, was one from which the miners of Cornwall 

 M'ere in the habit of exporting their minerals, and there is a small isle (St. 



