attractive, from the beauty of its form, is the Coscino- 

 discus, or sieve-like disc, found ahke near Cuxhavcn, 

 at the mouth of the Elbe, in the Baltic, near Wismar, 

 in the guano, and the stomachs of oysters, scallops, 

 and other shell-fish. Another large deposit is found 

 at Andover, Connecticut ; and Ehrenberg states that 

 similar beds occur by the river Amazonj and in great 

 extent from Virginia to Labrador." ^ 



The testimony of Sir Joseph Hooker may be ad- 

 duced as to the formation of like deposits in recent 

 times in the Southern Hemisphere. " The Phonolite 

 stones of the Rhine and the Tripoli stone contain 

 species identical with what are now contributing to 

 form a sedimentary deposit (and perhaps at some 

 future period a bed of rock) extending in one con- 

 tinuous stratum for four hundred measured miles. I 

 allude to the shores of the Victoria barrier, along 

 whose coasts the soundings examined were invariably 

 charged with Diatomaceous remains, constituting a 

 bank which stretches two hundred miles north from 

 the base of the Victoria barrier, while the average 

 depth of water above it is three hundred fathoms, or 

 one thousand eight hundred feet." ^ 



They abound also amongst the pancake ice of the 

 South Pole, as far south as seventy-eight degrees, 

 where they must occasionally be subject to a very 

 low temperature. Though much too small to be 

 discernible by the naked eye, they occur in such 

 countless myriads as to stain the berg and pack ice, 

 wherever they are washed by the swell of the sea ; 



' Jabez Hogg, "The Microscope," p. 433. (1867.) 



' Berkeley, " Introduction to Cryptogamic Botany," p. 127. 



