CRUSTACEA OF NEW ZEALAND. 253 



or irregular beds of sliiagle and sand composing tlie plains, at least in the Ashburton 

 district. Some of the beds are intensely hard and extremely difficult to pierce with the 

 steel-pointed pipes. After the lowering of tlie water, Mr. Dolman ascertained when 

 driving the pipes to unusual depths that the pipe frequently entered ' dry-beds,' and he 

 had either to draw up or lower the pipe to tap the water. The deepest well he has 

 driven is 65 feet, and it lias continued to give a good flow ever since it was driven. 

 Mr. Dolman states that there is no limit, so far as he knows, to the depth the water is 

 found in the plains, although it flow^s in thinner or shallower streams the lower he sinks. 

 Referring to the discoloration of some streams, he informed me that he has found small 

 round particles of clay in the water, and he attributes its discoloration to these floating 

 particles. When sinking open wells, Mi\ Dolman has occasionally observed the direction 

 and rate at which the subterranean water flows. He estimates its motion at from one- 

 quarter to one-half a mile an hour. One important fact he has several times ascertained, 

 when driving the pipes through the lower and harder beds, is the rising of the w^ater in 

 the pipe to various heights from the newly-tapped stream. He has known it to rise 

 from 2 feet to 14 feet, and afterwards to remain permanent. There is considerable 

 difference in the work of sinking the various wells — some are put dow n in a few hours, 

 the pipes driving freely, and others require as many days, and this sometimes with a 

 heavier ' monkey ' at work. These facts can be better studied by an examination of the 

 high sections of the plains at the mouths of the Rangitata and the Ashburton Rivers. 



" The exceptional well I have mentioned, which did not become dry, is driven 27 feet, 

 and is in a low-lying part of the town. Nearly all the pipe-wells originally driven were 

 sunk to vai'ious depths, ranging from 15 feet to 22 feet. These, without any exception, 

 became dry." 



VII. Origin of the Subterranean Crustacea. 



In considering the source from which the subterranean Crustacea have been derived, it 

 will be well to state first what little is known of the freshwater forms of the Amphipoda 

 and Isopoda found in New Zealand and Australia. 



In New Zealand only one freshwater Isopod is known, Idotea lacustris, G. M. Thomson 

 [21, p. 263], and this one has no connection whatever with the subterranean fauna. In 

 Australia, however, a species of Phreatoicus is known, P. australis [20], as yet found 

 only on the top of Mt. Kosciusko, about 0000 feet above the sea. In the Amphipoda 

 w^e have two freshwater species recorded from New Zealand. One, CaUiopius jluciutllis, 

 is very common in almost all running streams of the South Island ; but is also found in 

 various places in Otago Harbour, in water that is quite salt. This species is very abim- 

 dant in the surface-streams of the Canterbury Plains, in the localities where the subter- 

 ranean forms also abound ; but, as I have already pointed out, although it approaches 

 CaUiopius suhternuieus, it is dissimilar in several respects, and it does not seem at all 

 likely that C. subterraneits is directly descended from it. The other species is Fheruna 

 cwrulea, G. M. Thomson [107, p. 200], found by Mr. Thomson on the top of the Old Man 

 Range, 3000 feet, in Otago, and as yet known from this locality only. I have compared 

 this species in some detail with CaUiopius subterraneus (see above, p. 235), and have 



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