336 THE CANADIAN NATURALIST. [Sept. 



value where we must in the state of the science know the sexes to 

 ascertain genera." 



The above gives some general idea of his correspondence with 

 Hentz, Melsheimer, Doubleday, Herrick, Say, Le Conte, and 

 othei's. Through all his writings there is traceable that persever- 

 ance and clearness of decision, which marks the true naturalist. 

 The familiar, popular, yet truly scientific style of its reasoning 

 will recommend the '' Correspondence of Thaddeus William 

 Harris " to all lovers of Natural History. 



The volume contains, also, descriptions of larvae, their meta- 

 morphoses, habits, &c. ; selected descriptions of insects ; re- pub- 

 lished papers, and contributions to entomology heretofore scattered 

 in different works, and not easily obtained. A. S. R. 



GEOLOGY AND MINERALOGY. 



Fossil Bivalved Entomostraca. — No one has done more 

 than Prof T. Rupert Jones to illustrate these numerous and 

 curious fossils, often microscopic, sometimes liable to be mistaken 

 for Bivalved Mollusca, which abound in stratified rocks of all 

 geological ages, and sometimes contribute not a little to the mass 

 of strata of some thickness. In the following paper, from the 

 Quarterly Journal of Microscopical Science, he clearly describes 

 their characters, affinities, and geological relations : — 



" On this occasion I have to explain the nature of the microscopic 

 Bivalved Crustaceans, to allude to their ways of life, and to draw 

 attention to some of the facts connected with their being found 

 fossilized in clays and stones. 



The common Crab and Lobster are important members of the 

 Crustacean group of Animals ; so also are Shrimps, Prawns, 

 Sandhoppers, Woodlice, the King-crab of the Moluccas, and 

 many others, which are only noticed by the naturalist and seen 

 in museums. 



A characteristic feature of the Crustaceans is their jointed 

 structure (placing them among the Articulata or Arthropoda), 

 and their being for the most part coated with a hard, tough 

 armour — the part that covers the front of the body being usually 



