I30 FAUNA HAWAIIENSIS 



due to the very great variety of suitable situations afforded, assuming, as Is most 

 probably the case, that the larval food consists of lichens. Probably a humid insular 

 climate is particularly favourable to them, provided it is also sufficiently cool ; the 

 latter condition can be secured by increased altitude, but a low-lying tropical island 

 would not be favourable. After making allowance for such local circumstances, how- 

 ever, there remains an excess of development of the genus in New Zealand and 

 the Hawaiian Islands, which does not seem explicable merely by favourable conditions. 

 Early occupation of the ground must have been the other factor in this result, and 

 probably at something like the same period in both island-groups, and this would 

 imply a common origin. Now the Hawaiian species are characterised by an unusual 

 tendency to narrowness of forewings, and by generally showing a few long hairs in 

 the cell of the hindwings ; both which characters are also repeated in a section of 

 the New Zealand species, and not in those of any other region. The New Zealand 

 species as a whole display a much greater variety of size and facies than any others, 

 and must be regarded as primitive in type and unspecialised. Two or three Australian 

 species of similar character doubtless claim a New Zealand origin. The Patagonian 

 S. chordactis, however, and one or two other species from neighbouring portions of 

 South America, which are undoubtedly closely related to peculiar New Zealand types, 

 are not so easily explained, but must be classed with the considerable body of other 

 evidence showing an ancient interchange of fauna and flora between South America 

 and New Zealand. An elevation of i loo or 1200 fathoms in the bed of the South 

 Pacific Ocean would be required, to allow of this being easily effected ; it is a large 

 demand, but cannot be said to be impossible. My present opinion, on the available 

 evidence, is that Scoparia originated in the New Zealand region, probably at that time 

 considerably extended. The Hawaiian Islands must then have received their original 

 species from New Zealand direct, and I should suppose that Christmas Island must 

 have been on the line of transmission, and would probably still possess allied species 

 as evidence thereof. 



These three genera are then respectively American, Asiatic, and New Zealand. 



(_/) Endemic genera, with i or 2 species. 



A class comprising 7 genera and 9 species. 



Nesamiptis contains two nearly related species ; it is most allied to Uypeiia, which 

 is extensive and very generally distributed, but apparently approaches especially the 

 type of some North American species. 



Progonostola is almost certainly an endemic derivative of Xanthorkoe. 



Sisyrophyta is undoubtedly an offshoot of Scotorythra. 



Tritocleis is at present of quite uncertain afiinity, and must be neglected. 



Genophanhs is certainly nearest to the monotypic Australian Crocydopora, which 



