GEOLOGY OF NEW ZEALAND. 445 
the following land and fresh-water shells—Thalassia obnubila (Reeve), 
and Limnea leptosoma (Hutton); the former is now common near 
Dunedin, but requires damp bush to live in; the latter is not known to 
be living in the South Island, but is found near Wellington. 
Pluvial Epoch.—The mollusca of the north of New Zealand differs 
sufficiently from those of the south to make any migration which might 
take place in either direction easily distinguishable. But there is 
nowhere any trace of such migration. Neither are there any signs of a 
pleistocene glaciation of New Zealand greater than at present. Conse- 
quently there is no evidence to shew that the high eccentricity in the 
earth’s orbit that took place in pleistocene times produced a glacial 
epoch in New Zealand. But there are several facts which appear to 
support the view that this high eccentricity produced a pluvial epoch, 
by causing greater winter snowfall, and greater summer floods. In the 
first place the occurrence of the bones of Apteryx as well as those of the 
water-loving Sphenodon, with bones of the moa at Hamiltons—in 
addition to the evidence of the trunks of trees themselves still lying on 
the mountains—all go to shew that the dry interior region of Otago 
was at a comparatively late date, covered with luxuriant forest. 
Secondly, the extraordinary agglomeration of moa bones in the turbaries 
at Glenmark, Hamilton’s, and other localities, where hardly even two 
toe bones were found in their proper places, can only be accounted for 
by heavy floods sweeping these bones up and depositing them in the 
low ground. And thirdly, the silt or “loess” of northern Otago and 
Canterbury, usually unfossiliferous, but sometimes containing moa 
bones and only stratified in its lower parts, seems to imply a very rapid 
accumulation caused by heavy and often recurring floods sweeping away 
the fine mud left by the retreat of the glaciers during subsidence, and 
its deposition in the sea. 
MHolian Deposits—Sand dunes are well developed in many places 
round the coasts of New Zealand, sometimes forming hills 500 or 600 
feet in height, as between Manukau Harbour and the Waikato, where 
they are cemented into hard rock by iron oxide derived from the black 
iron sand. These dunes often contain moa bones as well as traces of 
man. No less than eighteen species of Dinornis have been found in 
New Zealand, all of which have been described, more or less fully, by 
Sir R. Owen. Of these eighteen species, five are only recorded from 
the North Island, nine only from the South Island, while four are 
common to both Islands. 
Igneous Rocks.—The oldest of our igneous rocks are found in the 
Manipouri system in the West Coast Sounds, in the form of dykes of 
white granite, eurite, &c. They do not penetrate any higher, and no 
igneous rocks have been described as belonging to the Takaka system. 
The granites found at Preservation Inlet, and along the anticlinal axis 
through Westland and Nelson, have penetrated the rocks of the Maitai 
system, but are found as rolled fragments in the rocks of the Hokanui 
system down as low as the Kaihiku series. Their eruption therefore 
must have taken place towards the close of the Maitai or possibly 
during the interval between that and the Hokanui system. Dykes of 
syenite, diorite, olivine rocks, and serpentine are found in various 
localities in rocks of the Maitai system, and may be of the same age as 
the granite, and as these are in places accompanied by beds of green- 
