516 



TAXONOMY 



mal kingdom. These two kingdoms are further divided. Cer- 

 tain outstanding likenesses enable a scientist to divide the plant 



Museum of Natural History 



The Crustacea vary in size and shape from microscopic representatives to lobsters weighing 



nearly fifty pounds. 



kingdom into four divisions called phyla (singular, phylum). In 

 this book the animal kingdom will be divided into ten phyla. 

 The various phyla have been carefully analyzed and compared, 

 and finer groupings, called classes, made. Again a finer sorting 

 is made and the classes are split into orders. Certain char- 

 acters again permit a subdivision of the orders into genera. The 

 genera are separated into groups showing very close relationship. 

 These are the species. They are very much alike, but may still 

 differ slightly in form, habitat, or distribution. 



One phylum of animals, the arthropoda, is distinguished from 

 the other ten phyla in that all of its members are segmented, 

 have an exoskeleton and jointed legs. One of the classes of the 

 phylum arthropoda has a characteristic exoskeleton impregnated 



