528 Miscellaneous. . 



a tolerably distinct impression of a fossil shell in it, wliicb. may 

 perhaps be sufficiently distinct to enable its name to be ascertained. 

 Fragments of Carboniferous Limestone were not uncommon in this 

 sand-pit. From its position it is not easy to say for certain whether 

 it overlies or underlies the clays at Wyddfyd Farm. It has been 

 dug into to a depth of some eight or nine feet. I have sent speci- 

 mens of all the above-mentioned deposits, in the hope they may 

 throw some little light upon their origin. 



J. M. Mello. 

 St. Thomas' Paesonage, 



Brampton, Chesterfield. 



3vi:n:sc:HiXiXj.A-3^:E30TJS. 



DiscovEKT OF A Mew Mineeal (" Ckookesite "). — Whilst ex- 

 amining the seleniferous minerals from the Skrikerum mine, in 

 Sweden, M. Nordenskiold has discovered that thallium exists in 

 small quantities in eucairite ( (Cu Ag) Se) and berzelianite (Cu Se). 

 Continuing his researches among these selenides, in Mosander's col- 

 lection, he has found a mineral which contains from seventeen to 

 nineteen per cent, of this metal. It occurs in small opaque masses, 

 having a metallic lustre and lead-grey colour, mixed with the grains 

 of eucairite and berzelianite. From these it is easily separated, and 

 on analysis gives the formula (Cu, Tl, Ag) Se. Density = 6-9. No 

 crystalline faces yet observed. Before the blowpipe it fuses easily 

 into a shining greenish-black enamel, and the flame is coloured 

 intensely green. Insoluble in hydrochloric acid, but nitric acid 

 dissolves it completely. M. Nordenskiold has named this new 

 mineral " Crookesite," after the well-known discoverer of thallium. 

 But few specimens have been yet found of Crookesite, but M. Nor- 

 denskiold hopes to obtain more by carefully searching the Skrikerum 

 mine, which has been for some time abandoned. — T.D. 



A King-Crab in the Upper Silurian. — Among the fossils ex- 

 hibited by Mr. Eobert Slimon at the meeting of the British Associ- 

 ation in Dundee, and collected by him at Lesmahagow, in Lanark- 

 shire, was a minute form of Crustacean, nearly allied to Belinurus, in 

 which all the body segments appeared to be free and unanchylosed. 

 In calling attention to this beautiful little fossil, Mr. Woodward 

 pointed out the great interest attaching to its discovery, as being the 

 oldest representative of the Xiphosura, or King-Crabs, known, carry- 

 ing this division back in time from the Coal-Measures to the Upper 

 Silurian. 



Erratum in Mr. Forbes' Article in the October Number. 

 On p. 443, in footnote, in line 21 from foot of page, for " before," read after. 



