Corresjjondence — A. R. Hiott. 285 



by the phenomena described. No mention is made of a theoiy which 

 would, I tliink, remove the chief difficnlties mentioned. I suggest 

 that the true explanation is deformation plus chemical segregation. 

 The author rejects deformation (1) because the minerals are not 

 deformed. But this is not to be expected in a rock which has 

 undergone advanced metamorphism. The author assumes that the 

 minerals are original, whereas the rock may have been transformed, 

 as in the Malvern Hills, where some of the gneisses are entirely 

 composed of secondary minerals, and show no trace of the deforma- 

 tion which was evident enough in an earlier stage of the meta- 

 morphism. The author objects (2) that the minerals whose 

 distribution are the chief cause of the foliation are not " such as 

 to have been produced " by earth-movements. I cannot see why. 

 During the reconstruction of the rock the segregation of the 

 carbonates of lime and magnesia may well have been accompanied 

 by the cr^'stallizing out of the accessory lime and magnesia silicates.. 

 The hypothesis I have suggested accounts for three facts which 

 appear to have caused considerable perplexity, viz. : (1) the isolated' 

 masses of granulite, (2) the lenticular form of some of the granulite 

 masses (one would like to know if any of the limestones are 

 lenticular), and (3) the subordination of the limestone to the silicate 

 rocks. The theory of the origin of limestones by segregation from 

 plutonic rocks during deformation, as in the case of the crystalline 

 limestones of Bodwrog and Forth Trecastell in Anglesey (Eeport 

 Brit. Assoc, 1887, p. 706), has not yet, I think, received the: 

 consideration it deserves. C. Callaway. 



Cheltenham. 



ON THE OCCUERENCE OF SCALARIA COMMUNIS IN THE RAISED' 

 BEACH ON THE THATCHER ROCK, AND OF PECTEN iMAXUfUS 

 AND VENERUPIS, sp., AT HOPE'S NOSE. 



SiK, — In the year 1888 I published in the Transactions of the 

 Devon Assoc, a list of shells found in the Raised Beach on the- 

 Thatcher Rock in Torbay. 



In due course I sent a reprint to my friend and colleague the 

 late Mr. D. Pidgeon, F.G.S., which Mr. Pidgeon took the practical 

 and ingenious course of retui'ning to me crowded with copious 

 comments and criticisms. As Mr. Pidgeon took the extreme line 

 of denying the genuineness of the Raised Beaches, and I did not 

 feel disposed to seriously entertain tliis objection, I laid my friend's 

 notes on one side and forgot all about them. 



Last Easter, in looking for a copy of my paper for a friend joining 

 the excursion of the Geologists Association to the Gower Caves, 

 I found Mr. Pidgeon's returned copy. In it I discovered a rather 

 important fact, viz., an additional shell to what I believe is already 

 the record list for any one Raised Beach, viz., Scalaria communis. 

 Mr. Pidgeon also added his initials to Aporrhais pes-pelecaniy 

 a species before certified by Mr. J. T. Marshall. Scalaria com- 

 munis makes the grand total of species from the Thatcher beach 44, 

 a total which made Mr. Pidgeon remonstrate, " there are a great 



