632 ON SOME PAUROPODA FROM N. S. WALES, 



segments. The first covers the first and second segments, i.e., that 

 with only limb-rudiments, and that bearing the first legs. The next 

 four each cover two leg-bearing segments. In the case of the last, 

 though the anal segment projects freely behind, its anterior border 

 usually passes under the shield ; and, in a lateral view of F. 

 amicus (PL Ixx., fig. 10) this insertion is very obvious. This inter- 

 pretation would have the advantage of giving a uniform series of 

 double tergites, and may possibly, as has been indicated above, also 

 apply to the head. 



The contention, that the sixth shield is of a double nature, is sup- 

 ported, to some extent, by the condition of that shield in Eurij- 

 pauropus, the posterior part being marked off from the anterior 

 b}^ two lateral clefts. Ryder (1879, a) claimed these clefts as evi- 

 dence of the double nature of the shields; but Kenyon (1895, p. 91) 

 doubts the segmental significance, and suggests that the clefts are 

 formed "merely because the tactile hairs would otherwise be pre- 

 vented from projecting upwards in a position to be of greatest use 

 to the animal." I am inclined, however, to agree with Ryder. The 

 clefts are not necessary for the tactile setaB, as these might just as 

 easily be situated on the shields, as they are in Pauropus. 



The supposed diplopod condition of the Pauropoda does not 

 seem to me to be in any way comparable with that of the millipedes. 

 The double segments are certainly formed in a totally different way, 

 and, in the case of the Pauropoda, fusion is confined to the dorsal 

 shields. This fusion, I consider to be purely secondary, and to 

 have been brought about by a series of thickenings of the dorsal 

 cuticle, which Avere, at first, segmental, as we can see in Br achy - 

 pauropus; and which, later, without segmental significance, fused 

 in pairs. Pauropus is an animal with twelve, distinct trunk-somites, 

 the value of which is wholly independent of the dorsal shields. 



Nevertheless, the affinities of the Pauropoda are pretty cer- 

 tainly with the Diplopoda, and they are possibly best regarded as 

 an equivalent Order. It seems unnecessary to raise them to Class- 

 rank (Pocock, 1911) ; and not yet justifiable, in the light of present 

 knowledge, to reduce them to the rank of a Suborder, sharing, 

 with Polyxenus, an Order, Protodiplopoda (Kenyon, 1895). 



