J anna)')' gt/i, /poo.] P ROCK ED IN OS. 



XI 



repairing. Two examples occurred, both somewhat im[)erfect, 

 of similar form and style of marking, but different in coloration, 

 one being much paler than the other, but a third specimen was 

 unfortunately missed, this being reported as at least 7 inches in 

 length, whilst the type is barely 5 inches. 



'1 ne discovery of this marvellous species, one of the most 

 select not only of all Cw//but of all marine molluscs, is sufficient 

 to mark an epoch. 



Mr. Mark Stirrup, F.O.S., exhibited, for comparison with 

 Mr. Melvill's arctic shells, a collection made by him at Tromsoe, 

 the shells of the same species being all larger. 



Mr. Mark Sykes, P\R.M.S., drew attention to the Agave 

 ainericana, planted in 1S41 at Wmthorpe, near Newark, which 

 flowered for the first time this summer and then withered up. 



Ordinary Meeting, January gth, 1900. 



Osborne Reynolds, M.A., LL.D., F.R.S., Vice-President, 

 in the Chair. 



The thanks of the members were voted to the donors of the 

 books upon the table. 



Mr. Thomas Thorp exhibited two film-gratings of a ruling 

 designed to weaken the direct image and to condense the 

 illumination in the spectra of the first and second order, and thus 

 to compete with the prism spectrum in brilliancy. 



The President (Professor H. Lamb, F.R.S.) read a paper 

 entitled *' Geometrical Representation of the Relation 

 between Wave-Velocity and Group-Velocity. 



The paper is printed in full in tne Memoirs. 



Professors Reynolds and Boyd Dawkins and Mr. Stromeyer 

 participated in the discussion which followed the reading of the 

 paper. 



