1818.] Linruzan Society. -71 



their centre. The surfaces of the first species are smooth and 

 brilliant, while those of the second are dull and finely furrowed. 

 M. Vauquelin has found a difference in the chemical constituents 

 of the two species. Crystallography appears to admit as the 

 primitive form of mica either a right or an oblique rhombic prism. 

 Is it not probable that these may be the respective primitive 

 forms of the two species ? 



On Wallerite, or Linzinite. — Dr. Dufour, of St. Sever, Dept. 

 des Landes, has lately discovered near that place, in a bed of 

 clay, a substance externally resembling lithomarga. It appears, 

 however, from an analysis of it by M. Laugier, to contain 



Silex 32 



Alumine 37 



Water. . 27 



Sulphate of lime .... 3 



99 



It may, therefore, be considered as a siliceous hydrate of 

 alumine. 



LINNJEAN SOCIETY. 



May 5. — A continuation of the Rev. Mr. Kirby's century of 

 new insects was read. 



May 25. — The following is the list of officers for the ensuing 

 year. 



President. — Sir James Edward Smith, M.D. 



Vice Presidents. — Samuel Lord Bishop of Carlisle ; Aylmer 

 Bourke Lambert, Esq.; William George Maton, M.D. ; Edward 

 Lord Stanley. 



Of the Council, in Place of Jive Members %oho go out. — John 

 Duke of Bedford ; Mr. Andrew Forster ; Thomas Andrew 

 Knight, Esq. ; Thomas Reynolds, Esq. ; Sir George Thomas 

 Staunton, Bart. 



Treasurer. — Edward Forster, Esq. 



Secretary. — Alexander M'Leay, Esq. 



Under Secretary. — Mr. Richard Taylor. 



June 2. — A paper was read, by Capt. Carmichael, on the genus 

 pandanus. 



June 16. — A letter was read, addressed to the Rev. Mr. Kirby 

 by the Rev. Revett Sheppard, on the position of the toes in 

 certain genera of birds. 



The woodpecker tribe have four toes on each foot, two before 

 and two behind, which arrangement, according to Ray and all 

 subsequent naturalists, is for the purpose of enabling them to 

 climb with facility. According to Mr. Sheppard, there are six 

 genera of birds pedibus scansoriis, viz. psittacus, cuculus, picus, 

 rhamphastus, trogon, andbucco. 



The common cuckoo, which is one of these, though furnished 

 with two toes before and two behind, is never known to climb at 

 all ;, while the nuthatch (sitta europea) and tree creeper (certhia 



