| A comparative study is made of four chelicerate classes: Apatellata (Solifugae and Pseudoscorpionida), Arachnida s. str. (both groups of Uropygi, i.e. Holopeltida and Schizomida, Amblypygi and Araneida), Scorpionida and Xiphosura. Methods, principles and terminology, adopted in this paper, correspond with those of parts I -111 of the present series of comparative studies in Chelicerata. Special attention is paid to segmentation of the body, respiratory organs, orifices of coxal glands, mouthparts, and appendages. The evolution of these structures is studied, and the relationships of the chelicerate classes and subclasses are reinvestigated and discussed. |
