ALG.'E. 187 



Wc take Into account the ]arge number of num- 

 mulites and other distinctly animal shells, belonging 

 to dead foraminifera, which go to form masses of 

 limestone rock, and which are often referred to under 

 the vague title of infusorial remains. It is sufficient 

 for our purpose to demonstrate that immense beds, 

 many miles in extent, in different parts of the world, 

 arc entirely composed of diatoms. The material best 

 known is that called cementstein, from the island of 

 Mors, a large island in Liimfjord. This fjord, the 

 most extensive in Jutland, runs from east to west, 

 connecting the North Sea with the Kattegal. The 

 cementstein from Mors resembles a dark-grey slate, 

 interspersed with white veins. The siliceous organisms 

 of which it is chiefly composed are held together by 

 a calcareous cemejit, and when submitted to the 

 action of acids are slowly disintegrated with efferves- 

 cence. A similar deposit occurs in Fuur ; it is, how- 

 ever, more difficult to separate,and but slightly affected 

 by acid, and resembles the deposit known as "brown 

 coal." A third deposit is found in Nijkjobing, a small 

 town or village on the western side of Mors Island. 

 This deposit is of a greyish-white colour, still more 

 difficult to reduce than the preceding, strong acids not 

 affecting it in any appreciable degree ; and only by 

 the assistance of caustic potash or soda can the 

 organisms of which it is composed be effectually 

 separated. The Mors deposit, with perhaps one 

 exception, is richer in bizarre and beautiful diato- 

 maceous forms than any other hitherto discovered.^ 



' See " Diatomaceous Forms from Jutland," by F. Kitten, in 

 Qttekett Microscopical fournal ix'i-iO), vol. i. p. 99. 



