CLASSIFICATION OF THE ANIMAL KINGDOM 



Myzostomida. The two orders are ac 



34 



cepted from Prenant in the Traite de Zo- 

 ologie (1959). 



Annelida. Many recent books list the 

 Polychaeta and Oligochaeta as separate 

 classes. The differences between the two 

 are largely relative, and the two together 

 can be described in detail with few con- 

 flicts. For this reason, the two groups are 

 here combined in the class Chaetopoda, 

 as in many of the older works. Their dif- 

 ferences may then be brought out at the 

 subclass level. 



No really satisfactory classification of 

 this phylum or its classes has been found. 



Polychaeta. The usual division into 

 two orders has been followed, with the ad- 

 dition of one extinct order. 



Oligochaeta. There being no generally 

 accepted subdivision of this group, the one 

 given without Latin names by Avel (1959) 

 in the Traite (attributed by him to Mi- 

 chaelson, 1930) and without acceptable 

 single names by Pearse (1949) is followed 

 here. The names are emended to conform 

 to custom in Latin nomenclature. 



Hirudinea. Division of this class into 

 four orders was proposed by Harant & 

 Grasse (1959) using three orders pro- 

 posed by Caballero (1952) and adding the 

 "Acanthobdelliformes nom.nov." These 

 names and groupings were not new there, 

 except in ending. Rhynchobdellida dates 

 from Blanchard (1887), Gnathobdellida 

 from Vaillant (1890), and Pharyngobdel- 

 lida from Johannson (1913). These same 

 four orders were recognized by Lowenstein 

 (1954), using the name Acanthobdellida 

 and using the name Herpobdellida instead 

 of Pharyngobdelliformes. 



It is not clear whether these names 

 were independently proposed, but there 

 seems to be no need for the -iformes end- 

 ings here. The four orders are accepted 

 here, the spellings of Caballero and of 

 Harant & Grasse are rejected, and Pharyn- 

 gobdellida is accepted because of apparent 

 priority. 



Archiannelida. There is apparently 

 general agreement that there is only one 

 order in this class. No ordinal name is 

 available. 



Tardigrada. The division into three orders 

 in two classes is taken from Pearse (1949), 

 after Richters (1926) and Marcus (1927). 



Penlastomida. The orders are from Boett- 

 ger(1952). 



Onychophora. Division of the phylum 

 into two orders is accepted from Boettger 

 (1952) and the Treatise (O, 1959), fol- 

 lowing earlier writers. 



Arthropoda. Some recent classifications 

 of this largest of all phyla have been com- 

 plicated by attempts to include the Penla- 

 stomida, Onychophora, and even the Tar- 

 digrada. When this is done, the phylum 

 can no longer be defined, because it would 

 include a variety of body cavities, nervous 

 systems, respiratory systems, excretory 

 systems, integuments, etc. With these 

 groups removed, the arthropods can read- 

 ily be classified into eleven classes, and 

 these can be grouped into three subphyla. 



Much of the classification of the 

 Arthropoda above the ordinal level is in an 

 unsettled state. There seems to be no sin- 

 gle complete classification that is adequate 

 for both Recent and fossil groups. The one 

 presented here is therefore made up from 

 many sources, most of which are at least 

 in part drawn from earlier sources. Listed 

 below are the recent works that are ac- 

 cepted at each level, but they usually are 

 not the original proposal of the arrange- 

 ment. 



Subphyla are accepted from Pearse 

 (1949), classes in the Trilobitomorpha 

 from the Treatise (O, 1959), in the Che- 

 licerata from Pearse (1949) and Moore 

 (1952), and in the Mandibulata from 

 Pearse (1949) with exclusion of super- 

 classes. 



Orders in the Trilobitomorpha are 

 from the Treatise (O, 1959), in the Mero- 

 stomata from the Treatise (P, 1955), in 

 the Pycnogonida from the Treatise (P, 

 1955), in the Arachnida from the Treatise 

 (P, 1955) which is the system of Petrunke- 

 vitch, in the Crustacea from Waterman & 

 Chace (1960), in the Pauropoda and Sym- 

 phyla from Brues & Melander (1954), in 

 the Diplopoda from Boettger (1952), in 

 the Chilopoda from Pearse (1949), and in 

 the Insecta from Brues & Melander (1954). 



The class Eurypterida consists of a 

 single order, for which the synonym Gi- 

 gantostraca can reasonably be used. 



Clicu'ioi^natlia. This is another of the one- 

 class one-order phyla. Boettger (1952) has 

 used the name Sagittoidea for both class 

 and order, but it seems to be more appro- 

 priate to restrict this name to the ordinal 

 level and to use the phylum name also at 

 the class level. The other two synonyms 

 seem to be inappropriate as they were 



