334 ORTMANN — DISTRIBUTION OF DECAPODS [April 3, 



formula and shape of gills, is entirely unknown ; a figure of this 

 very important form is also missing. 



But taking it for granted that the genus Parastacus itself is found 

 in the Fiji Islands, and that Astaconephrops in New Guinea is 

 closely allied to it, this would indicate a connection of New Zea- 

 land with Australia by way of Fiji Islands and New Guinea. This 

 assumption appears, judging alone from this material, very poorly 

 supported, but it agrees well with other known facts which have led 

 to a similar theory. \ 



According to Hedley (1899), New Zealand was connected with 

 Australia in the following manner (see map, /. c. , p. 404). From 

 North Australia and New Guinea, which were united, a peninsula 

 extended over the Solomon Group and the New Hebrides, where 

 a smaller peninsula branched off in the direction toward the Fiji 

 Islands; and, farther, this main peninsula extended over New Cale- 

 donia, Lord Howe Island to New Zealand. Hedley calls this the 

 " Melanesian Plateau," and we may name it conveniently the 

 Melanesian Peninsula or Melanesia. As to the time of existence 

 of the latter Hedley does not express himself very positively, but 

 according to von Ihering (1894, p. 406), New Zealand and the 

 Fiji Islands became separated from Australia before the Eocene, or, 

 as may be gleaned from other places in his text, at the beginning 

 of the Eocene. 



The views of these two authors are founded exclusively upon 

 zoogeographical evidence, and we see that the genus Paranephrops 

 of New Zealand is apt to furnish additional support to Hedley's 

 Melanesian Peninsula. That this peninsula was disconnected from 

 Australia, not later than in the Eocene, also agrees with our mate- 

 rial. We have seen above that forms of the Parastacoid type must 

 have existed in Australia as early as in the Upper Cretaceous, and 

 thus nothing opposes the assumption that they immigrated into New 

 Zealand in Pre-Eocene times. 



Examining the tectonic and geological side of the question, we 

 have to refer first to the views propounded by Suess (1888, p. 

 181 ff.). According to him, the Alps of New Zealand are a com- 

 paratively old range, which existed probably as early as in Jurassic 

 times, and, further, he points out (/. c. , p. 203 ff.) the analogy in 

 the structure of New Caledonia and New Zealand. For the rest, 

 the islands between New Caledonia and New Guinea are too poorly 

 known in this respect, and, therefore, we cannot say^ anything 



