IREDALE : THE CHITONS OF THE KERMADEC ISLANDS. 4!) 



tlie Lord Howe and Norfolk Island species is strictly referalJe to 

 Sypharochiton. In any case it differs so much from the Kermadec 

 species as to discount any value it might seem to have with regard to 

 the zoological relations of the groups. 



The genus Rhyssoplax is well developed in Australasia, but we do 

 not know enoiigli about it to gauge the value of the occurrence of 

 a single species. Thus at the Kerraadecs was found a variable species 

 which is undoubtedly closely related to a species found at Norfolk 

 Island, but wliich does not occur at Lord Howe Island. My species 

 recalled to me Ch. cereus, Ileeve, from New Zealand, whilst Hedley 

 and Hull noted the relationship of theirs to the New Caledonian 

 Ch. discolor, Souverbie. In each case the relationship is somewhat 

 distant, and we cannot make any good comparison until the species 

 of this genus are better known. Thus the genus is represented on 

 Lord Howe Island by a species " not closely allied to any other 

 Australasian Chiton", as Hedley & Hull remark. 



A small species of Lncilhia was observed at the Kermadecs, though 

 not yet recorded from either of the other groups. 



At the Kermadecs occurred a species of Onithochiton undoubtedly 

 nearly related to the common Neozelanic species, whilst none was 

 observed at Norfolk Island. Hedley & Hull contrast the .species 

 found at Lord Howe Island with the Australian species, but probably 

 a nearer relative will be found in New Caledonia. 



My own conclusions regarding these Chiton faunas is that they are 

 each peculiarly distinct from each other, and, as I have advocated the 

 extreme value of this group as a factor in solving zoogeographical 

 problems, I would conclude as follows: — The Kermadec Chiton fauna 

 leaves no doubt whatever that its source is Neozelanic, the Polynesian 

 element being almost negligible. The genera Eudoxochiton, Plaxi2)hora, 

 Cryptoconchus, luark the tauna in an unmistakable manner. The 

 facts that the species of Plaxiphora must be classed in the Neozelanic 

 sub-genus Maorichiton, that the species of Onithochiton is unquestion- 

 ably only related to the Neozehinic species 0. Jilholi, Rochebrune, 

 whilst the .species of Sypharochito7i must also be considered of Neozelanic 

 origin, confirm the preceding unequivocably. 



The Norfolk Island Chiton fauna shows no characteristic forms, 

 but a slight relationship with the Kermadec and with the Lord Howe 

 species. Only five small species live there : the first, a LepidopletirKS, 

 of no value in this discussion; the second, an Acanthochites which is 

 considered identical with a Lord Howe species and its near affinit}' 

 indeterminable ; the third, an Ischnochiton very close to the Kermadec 

 species, but on account of tlie great resemblance of the s})ecies in 

 this group may prove less nearly related than is at present considered ; 

 the fourth, a Chiton, questionably a SypharoGhiton, which is merged 

 with the Lord Howe species. At present its nearest ally may be the 

 Kermadec Sypharochiton, but it is very different from that ; the fifth, 

 a Rhyssoplax, is nearest to the Kermadec species, but the value of 

 this affinity I cannot calculate with the available data. It is, however, 

 jemarkable that, omitting the Lepidopleurns, two Norfolk Island 

 species are considered identical with two Lord Howe forms, the 



VOL. XI — MAKCH, 1914. 4 



