ON THE ONYCHOPHORA OF WEST AUSTRALIA. 367 



20. Fauna of Western Australia. — II L Further Contributions 

 to the Study of the Onychophora. The Anatomy and 

 Systematic Position o£ West Australian Peripatoides, 

 withanaccount of certain histoloofica! details of general 

 importance in the study of Peripatus. By Wm. J. 

 Dakin, D.Sc, F.Z.S., F.L.S., Professor of Biology, 

 University of Western Australia. 



[Received March 16, 1920 : Read May 11, 1920.] 



(Plates I.-V.*) 



INTRODUCTION. 



There are yet manj'' details of interest in the structure of 

 Peripatus which remain problematic. The histology of the eye 

 and the structure of the trachefe may be cited as examples ; 

 whilst even the presence of cilia, an unusual character for an 

 arthropod, has been doubted by some histologists. 



In addition to general features, such as the above, there is 

 always the consideration that the anatomy of the diiferent species 

 of Peripatus should be thoroughl}^ well known, especially as in 

 many places there is a tendency for the advance of civilisation 

 and closer settlement to drive this somewhat rare animal to 

 extinction. It has been comparatively easy in Western Australia 

 for the author to procure specimens of this interesting group of 

 arthropods and the facilities for examining specimens being so 

 to speak on the spot, there seemed a likelihood that a close study 

 would reveal something new regarding the West Australian 

 species at least. Further support was lent to this view by reason 

 of the fact that one West Australian species, the first to be 

 discovered, had only been collected once many years ago, and was 

 very briefly and quite insutiiciently described. Practically no 

 details of the anatomy were known. 



In all, three species of Peripatus — or, perhaps more correctly, 

 PerijKitoides — have been i-ecorded from Western Australia, 

 namely : — 



1. Peripatus leuckarti, var. occidentalis Fletcher, syn. Peri- 



7jatoides occidentcdis Dendy. 



2. Peripatoides gilesii Spencei'. 



3. Peripatoides woodioardi Bouvier. 



. Of these three, Peripatoides occidentalis was the first to be 

 collected. It was discovered about 160 miles south of Perth, at 



* For explanation of the Plates, see p. 338. 



