280 Transactions. 



According to Hedley (6, p. 98), Heurteau was the first to recognize the 

 geological connection between New Caledonia and New Zealand, and the 

 subject was reviewed by Crosse (1, p. 443). I give here a translation of some 

 of his remarks : " Considered from a geological standpoint, New Caledonia 

 is a direct continuation of New Zealand, despite the enormous expanse of 

 sea now separating the two countries. We find the same Triassic, Jurassic, 

 and Cretaceous formations, disposed in similar order, containing analagous 

 fossils, and there is an abundance of eruptive rocks." There also exists 

 a close relationship between the animals and plants of New Caledonia and 

 New Zealand. In the Recent fauna there is the same absence of all mammals, 

 except bats and rats, and the same poverty of reptiles. Snakes are absent 

 from both, and the Amphibia consist of one in New Zealand and none 

 in New Caledonia. There is a close correspondence between Melanopsis, 

 Placostylus, Rhytida, Athoracophoridae, the Charopa group of Endodonta, 

 and some of the Phenacohelicidae, Rhytidopsis being nearly allied to our 

 Phenacohelix, and Monomphalus to our Allodiscus. The land Mollusca of 

 Lord Howe Island have a close affinity to those of New Caledonia (7, p. 403). 



Speaking of the Great Glacier Epoch of New Zealand, Hutton (8, pp. 176, 

 182) comes to the conclusion that an elevation of 3,000 ft. to 4,000 ft. would 

 be sufficient to produce the phenomena of the period of glaciation. In 

 the older Pliocene came the last great upheaval, all the islands were joined 

 together, and the land stretched away to the south, east, and north, reaching, 

 in a north-westerly direction, Lord Howe Island. A bank submerged to 

 a depth of about 1,000 fathoms extends from New Zealand to Lord Howe 

 Island, and represents the former Pliocene land extension. 



These short geological and faunistic considerations clearly indicate where 

 we have to look for the home of the ancestors of our Placostyli, which is 

 beyond a doubt Lord Howe Island, and indirectly New Caledonia. In 

 1854 Gaskoin described Placostylus bivaricosus (13, p. 25, pi. 12, figs. 1-4) 

 from Lord Howe Island, a species which is closely allied to the New Zealand 

 P. hongii, which had the name of the Maori chief Hongi Ika (born 1787 ; 

 died 1828) given to it by Lesson. The resemblance of the two species is 

 so great that Hedley was fully justified in writing, " This species (P. 

 bivaricosus) speaks eloquently of a recent land connection extending on 

 the one side to New Caledonia, on the other to New Zealand " (3, p. 140). 

 Etheridge holds that the nearest allies in New Caledonia are P. caledonicus 

 Petit and P. porphyrostomus Pfr. (2, p. 132). As already mentioned, Lord 

 Howe Island has a post-Tertiary Placostylus, which is found embedded in 

 coral-sand rock of aerial, not sedimentary, origin, and which was called 

 P. bivaricosus solidus by Etheridge (10, p. 27 ; 2, p. 131). This variety 

 is distinguished by the peculiarity of the peristome ; the outer and inner 

 lip broaden, exposing repeated laminae of growth ; the callosity on the body- 

 whorl thickens greatly, supporting strong tubercles and.emarginations. We 

 must, of course, conclude that this variety is the forerunner of P. bivaricosus. 



Now, we have in New Zealand a shell which, though somewhat larger, 

 corresponds very well with the subfossil Lord Howe variety — P. hongii 

 ambagiosus, which I described and figured in 1906 (11, p. 768). This sub- 

 species is found subfossil, but also still living, and this no doubt represents 

 the form which reached New Zealand from Lord Howe Island when the 

 former stretched far out to the north-west. On Lord Howe Island also 

 occurs a variety, P. bivaricosus etheridgei Brazier, which is a large, thin, 

 elongated form, with a simple, very little thickened peristome, which is 

 not notched (10, pi. v, figs. 1, 2, 7, 8). New Zealand possesses a similar 



