162 Transactions. — Zoology. 



multiporus, occurs in great numbers in a portion of an old 

 river-bed near Ashburton covered with only a fev/ inches of 

 soil. Their actions in such situations are a perfect illustra- 

 tion of their mode of covering the shingle-flats with mould as 

 they have done the plains in former ages, now elevated higher 

 above the rivers. Although some eight or more species of 

 native worms, ranging from lin. to 16in. in length, inhabit 

 the plains, the work of all was necessary to reduce the once 

 great expanse of shingle, sand, a^nd glacier-mud to the present 

 mould-covered, fertile state. The periodical flooding of the 

 rivers now traversing the Canterbury Plains is conducive to 

 the formation of soil on the shingle-flats over which the flood- 

 water spreads. The deposition of beds of unequal depths of 

 fine silt explains the cause of the uneven depth of soil cover- 

 ing some parts of the plains. An examination of sections 

 exposed on both sides of the rivers shows the same process or 

 action of the rivers to have proceeded continuously since they 

 commenced to cut their channels lower in the plains. During 

 the retreat of the glaciers the volume of water in the rivers 

 was immensely greater than now, while it flovv'ed at a higher 

 level, and spread out extensively over the plains. Occa- 

 sionally smaller streams branched off, leaving small plateaux 

 of shingle between them and the main stream. As the latter 

 wore their channels deeper the beds of the smaller streams 

 were silted up during high floods, often forming extensive 

 swamps. I have observed the Ashburton Eiver deposit 2ft. 

 and 3ft. of muddy silt during a single flood in these older side- 

 channels now elevated above the main stream. In a few 

 years a sparse vegetation grows in these silty or fine sandy 

 places, while the earthworms gradually advance, and work 

 them and the intervening shingly parts into areas of fertile 

 land. 



A broad shingly area is a formidable task for earthworms 

 to cover with soil ; yet such was accomplished by native earth- 

 worms on the now fertile Canterbury Plains. The late Sir 

 Julius von Haast, the illustrious geologist and explorer of New 

 Zealand, described the origin of the plains as follows : " With 

 the exception of some morainic accumulations in the upper 

 parts, and the drift-sands round Banks Peninsula, and the 

 partial lacustrine deposits filling the former extension of Lake 

 Ellesmere, the whole of the plains were formed by the deposits 

 of huge rivers issuing from the frontal end of gigantic glaciers." 

 In the same article also occurs the following : " We must con- 

 clude that the Canterbury Plains were formed by the outlets 

 of enormous glaciers, large torrents bringing down with them 

 the morainic matter thrown in their course at the terminal 

 face, raising their beds and shifting their channels at the same 

 time so as to form fan-shaped fluviatile accumulations con- 



