Ktrk. — Botany and Conchology of Great Omaha. 363 



robust and tenacious of our introduced plants have not established themselves 

 there. The few individuals which we find, appear there as intruders which do 

 not flourish, but exist as it were by sufferance. They would probably die out 

 altoojether were it not that neio^hbourinoc cultivations serve as centres of 

 propagation. As a matter of fact, the high road alone divides the area on 

 which I collected from another which has for a long time been under cultiva- 

 tion and sown with English grasses, and even in the very midst of the former 

 there existed at the time a paddock which had been twice ploughed, and was 

 then under a crop of oats. 



Art. L. — On the Botany and Conchology of Great Omaha. 

 By T. Kirk, RL.S. 



[Read before the Auckland Institute, 23rd September, 1872.] 



The harbour of Great Omaha is about forty-five miles north of Auckland, 

 lying nearly midway between Mahurangi and Pakiri. For the purposes of 

 this paper the district may roughly be sketched as extending from the 

 Matakana Falls to Little Omaha, the latter situate about eight miles from 

 Point Podney. 



The district is bounded on the west by the hills known as the Omaha 

 or Pakiri ranges, which attain their greatest altitude, 1,380 feet, at Mount 

 Hamilton, and are chiefly composed of sandstones overlying palaeozoic slates, 

 the latter often in a decomposed condition where exposed. 



An outlying range of no great altitude, extending from Mount Hamilton 

 to the head of the Matakana Piver, may be considered the southern boundary, 

 while the coast line from thence to Takatau Point, and inwards from the 

 mouth of the harbour to Little Omaha, will form its eastern side. 



Dioritic rocks occur at the entrance to the harbour and other places. 

 Fossil shells of several species are found at Kohuroa and Little Omaha j 

 amongst those collected in the latter locality is an immense Ostrea which 

 exhibits singular and varied forms. The southern boundary is marked by a 

 sharp conical peak of diorite which at once attracts the notice of the traveller 

 from the contrast it offers to the rounded summits of the adjacent hills. 

 From the base of the range, and extending to the inner waters of the harbour, 

 is a considerable extent of flat land, much of it swampy and intersected by 

 numerous small streams. The inner waters are separated from the ocean by 

 Whangatau, a peninsula of blown sand with a magnificent beach three miles 

 in length and half a mile in width at low water. The entrance to the 

 harbour is narrowed by a conical rock, which is exposed at half tide, but 



