272 POLYPI.ACOPHOHA (IF Lolil) IIOWF. AM) NOKFOLK ISLANDS, 



are common to eithci- the mainland of Australia or to New 

 Zealand, although two species are very closely allied to mainland 

 species. The shells are all of small dimensions, and the absence of 

 the large continental forms of Plaxiphora, Acanthopleura, Eudoxo- 

 chitun, and Lorica is remai^kable, especially as Plaxiphora and 

 Eudoxochiton occur on the Kermadec Islands. The absence of 

 Ischnochiton from I^ord Howe Island, and of Onifhochifon from 

 Norfolk Island is perhaps remarkable, but the latter genus may 

 yet be found at Norfolk Island in deeper watei- than that ex- 

 plored. No general resemblance to either Australian or New 

 Zealand forms can be definitely traced, but the fauna of both 

 Islands is related. Mr. Tom Iredale considers that the Chiton 

 fauna of Lord Howe and Norfolk Islands is nearly related to 

 that of the Kermadecs, and more distanth' to that of New Cale- 

 donia.* (Mr. Iredale had seen the specimens now described). 



The physical characters of both Islands are similar, both being 

 of basaltic formation, and both possessing coral reefs. Lord 

 Howe is the furthest south of the Islands having coral reefs. 



The Islands composing the Lord Howe, Norfolk, and Kermadec 

 groups ate small in size. Considering this, and the great distance 

 of sea which intei-venes between them, it is remarkable how much 

 their fauna has in common. And here the Polyplacophora repeat 

 conclusions drawn not only from the marine fauna in general, 

 but also from the terrestrial fauna and flora. Beyond this inter- 

 island affinity the fauna and flora next express a kinship with 

 those of New Zealand and New Caledonia. Lastly, the neigh- 

 bourhood of the Australia)! continent has made an impression, 

 especially on the nearer island. One of us proposed! to express 

 these conditions by grouping these Islands in a separate subregion, 

 the Philippian. 



The types of the new species here described liave been pre- 

 sented to the Australian Museum. 



* Iredale, Proc. Malac. Soc. ix., 1910, p. 162. 

 tHull, 'IMie Birds of f^ord Howe and Norfolk Islands. Kmn, xi., 1911, 



p 58, 



