3 Introduction 



universal acceptance in the near future. Indeed, even the ordinal endings 

 in -iformes adopted by American ichthyologists and ornithologists are 

 almost entirely unused in the rest of the world. The resulting names are 

 unnecessarily long and cumbersome. The system does not relieve any- 

 one from learning the shorter forms also. The latter are used here, with 

 the uniform-ending forms listed as synonyms. In other groups, usage 

 of the source of the classification is followed as to spelling, in most 

 cases. There are a variety of systems in use and no obvious trend to- 

 ward adoption of any single system. 



This classification attempts to show the various spellings as well as 

 the various synonyms. Each zoologist will choose which one he wishes 

 to use in each case. 



Seventh, no single rule will suffice for choice of names where several 

 apply to a single taxon. Reasons for each decision are given in the text 

 in many cases, but in general it has been the goal to retain the best 

 known names, at the most appropriate level, regardless of homonymy. 

 Priority is considered to be of secondary importance at these levels. 



Eighth, although considerable homonymy exists at all levels, even up 

 to that of phylum names, there is almost no real confusion caused 

 thereby. Until there are direct rules to govern the decisions, there seems 

 to be nothing gained by replacing well known names, such as Decapoda 

 (either in the Cephalopoda or in the Crustacea). 



This classification is in three parts, the purposes of which are quite 

 different. In order of preparation, these are: 1] the complete classifica- 

 tion, including lists of the phyla and of the classes and orders, of all ani- 

 mals, living and fossil; 2] the justification for unusual features in this 

 classification; and 3] a simplified classification of Recent animals for 

 student use, with common names, again including lists of the phyla 

 and of the classes and orders. The arrangement of these parts in the 

 book is just the reverse of this. 



In both lists, the phyla are first arranged in four subkingdoms, and 

 one of these is divided into four series. Many other groupings of these 

 phyla are possible, and several are shown in the footnotes of the section 

 Complete List of Phyla. It is not here believed that these supra-phylum 

 groupings are of much significance at this phase of the knowledge of 

 animals. 



In both lists of orders, these orders are arranged in the appropri- 

 ate classes and subclasses. No other levels, such as superorder, are rec- 



