BY R. J. TILLYARD. 41 



The excessively wet portion of tropical coast -line centred around 

 Innisfail, North Queensland, with a rainfall up to 130 inches a 

 year (nearly all summer rain) is not so rich in species as the sur- 

 rounding districts with from 50 to 70 inches. 



Other Applications of the Method. 



The Method of Specific Contours may be profitably used in 

 studying the density distribution of Zonal Groups — ^.e., groups 

 which are not confined to one zoogeographical region, but are 

 distributed along a zone of the earth's surface. On the map of 

 the world (Mercator's projection) contours ma}^ be shown of 

 Boreal, Holarctic, Bipolar, or Circumtropical groups which will 

 present at a glance the salient features of distribution in a graphic 

 manner. The author has worked out on these lines the contour 

 of the holarctic genus Ser}iatochlora with a very satisfactory 

 result, though the number of detailed records available was 

 scarcely sufficient to give a very accurate contour. Leaving out 

 of account three species usually included in the genus (two from 

 New Zealand and one from Chili) about whose inclusion in the 

 genus there is ground for doubt, we obtain a contour of the zonal 

 type ranging round the northern temperate zone. It is interrupted 

 by the Atlantic — as might be expected — but not by the Pacific, 

 since two species, at least, occur on both sides of Behring's 

 Straits, and extend far westwards into Siberia and eastwards 

 into Canada. The primary zoocentre seemed to be located in 

 the vicinity of the State of Maine, U.S.A., with a density of six 

 species, while a secondary zoocentre of large extent but of less 

 density (three) runs across the northern part of Europe and 

 Asia. The boundary line of the contour southward throws out 

 two well-defined projections into lower latitudes, one down along 

 the eastern coast of U.S.A. as far as Florida, another into Japan, 

 while a somewhat indefinite bulging takes place to include 

 records of a single species extending into Arizona. 



This contour is not published here, because the inequality of 

 the records available scarcely admits of its consideration in any- 

 thing but the broadest of aspects. More collecting has been 

 done in the one State of Maine than in the whole of Siberia. 



