Hare. — Additions to Perlidae, dc, of New Zealand. 33 



2 . DifEers from J as follows : Antennae not longer than forewings ; 

 pubescence of forewings almost wholly dark brown. 

 Length, 6 mm. Expanse of wings, 17 mm. 



Hah. — AVainuiomata River, Wellington. 



Hydrobiosis ingenua, n. sp. 



Brownish-fuscous. Antennae as long as forewings, brown. Maxillary- 

 palpi pilose, fuscous. Ocelli dark brown, distinct. Head, prothorax, and 

 mesothorax densely clothed with brown hairs. Forewings brownish - 

 fuscous, hairs lighter ; a pale - golden band before termen and a tuft 

 of black hairs on superior cubitus at ^. Hindwings greyish - fuscous, 

 strongly iridescent. Legs greyish-ochreous, tibise and tarsi marked with 

 fuscous, spurs brownish-ochreous. 



Length of body, 6 mm. Expanse of wings, 14 mm. 



Hab. — Wainuiomata River, Welhngton. 



Art. VI. — Notes on some Rocks from Parapara, Bluff Hill, and Waikawa. 



By J. Allan Thomson, B.A., B.Sc, F.G.S., A.O.S.M. 



Communicated by G. M. Thomson, F.L.S. 



[Read before the Otago Institute, lith September, 1909.] 



Introduction. 



The description of a few isolated rocks can seldom advance geological know- 

 ledge very greatly, and this paper must be regarded mainly as an attempt 

 to draw attention to some interesting regions of the Dominion, The day 

 has gone by when descriptions of new types of igneous rocks can attract 

 more than local interest, and petrologists are more and more tending to use 

 description only as a handle for the discussion of theoretical questions. The 

 two outstanding subjects of discussion are, — 



(1.) The nature of igneous magmas, the history of their consolidation 

 and their relations to neighbouring rocks, involving the theories 

 of differentiation, admixture of igneous magmas, and assimilation 

 of the walls of the magma-basins. 



(2.) The mode of formation of the crystalline schists. 



New Zealand is a country so rich in rock-tj^es, and so well provided with 

 natural sections, that it is not vain to suppose that much material may be 

 foimd which may throw important light on these philosophical questions. 

 Two such districts are outlined in the sequel. 

 2— Trans. 



