2^S KINGSLEY. [Vol. VIII. 



While the present is not the proper opportunity to support 

 the above classification in detail, a slight amount of explana- 

 tion seems necessary with regard to some of the novelties in- 

 troduced above. 



It has been shown, I think conclusively, that the relation- 

 ship existing between the Arachnida and the Xiphosures is 

 ■ very close ; that they have more affinities with each other 

 than, on the one side, the Arachnida have with the other 

 " Tracheates," or than Limulus has, on the other hand, to the 

 Crustacea. For the class formed by the union of these forms 

 I proposed, eight years ago, the name Acerata,i a modification 

 of the term Accra applied by Latreille to the Arachnida 

 alone. For the sub-class containing the Xiphosures and the 

 Eurypterina I have followed Dohrn in modifying and adopting 

 the term Gigantostraca of Haeckel. For essentially the same 

 group Packard has proposed at different times the names 

 Palzeocarida and Podostomata, while Steinmann and Doderlein 

 (Elemente der Palaontologie) have applied to the same associa- 

 tion of forms the term Palaeostraca. 



The resemblances between the Acerata and the Crustacea are 

 much closer than those between either and any of the other 

 groups of Arthropods, and from the fact that in each respiration 

 is effected by gills or by their homologues, developed in all 

 cases as membranous expansions of the limbs, the older term 

 Branchiata, used with enlarged scope, seems most applicable to 

 the group or sub-phylum formed by their union. 



The so-called Myriapoda seems to be a heterogeneous asso- 

 ciation of forms, polyphyletic in origin, and only associated 

 together through the possession of many locomotor appendages. 

 On the other hand, the resemblances between the Chilopods 

 and the Hexapods are far more numerous and of far more sig- 



1 Since this use of the term Acerata Lankester has employed it ('90) as equiva' 

 lent to the term Branchiata as limited in this article. Cholodkowsky ('91) objects 

 to my group Acerata apparently more upon the inapplicability of the term than 

 from any objection to the association of the Arachnids with the Xiphosures. As 

 I think I have strengthened the ground for such union in the present article a 

 name for the group becomes necessary, and as in both the Xiphosures and the 

 Arachnids functional (if not morphological) antennas are entirely lacking, I may 

 be permitted to continue the use of the term. 



