142 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



gradual pitch in the continental slope, and there is nothing to indicate 

 that the outer Barrier Reef patches rise from very great (" unfathom- 

 able") depths. On the contrary, the outer reef patches are all well 

 within the 100 fathom line, and at a distance from it, except where the 

 pitch of the continental slope is unusually steep. The inner reef patches 

 all come up from a line which cannot be of greater depth than about 

 twenty fathoms, that being the average depth of the first inner chan- 

 nel between the outer patches of the Barrier Reef and the outer line of 

 inner reef flats. The inner line of reef flats rises from a lesser depth, 

 not more than ten to fifteen fathoms. The section lines passing froni 

 the mainland to the line of outer barrier reef, across high rocky islands 

 and reef flats, indicates that the coral reef rock and coral reefs can only 

 constitute a comparatively thin sheet from the outer line of inner reef 

 flats towards the mainland, and that this sheet probably does not extend 

 beyond the lower slope of the islands which they surround, and the 

 base of which is formed by the submarine extension eastward of the 

 strata of the continental slopes. And furthermore that the outer barrier 

 reef probably does not rise from a much greater depth than that at 

 which reef-building corals can flourish. 



Kent has followed very much the same line of argument as Jukes, in 

 assigning the formation of the Great Barrier Reef to the depression (in 

 recent times) of the northern part of the Australian continent, — a de- 

 pression, however, which must have taken place during cretaceous times. 

 But he lays no stress on the connection which must have existed in 

 comparatively recent times between Australia and Xew Guinea, during 

 the early part of the formation of the Great Barrier Reef, — a connection 

 fully recognized by Jukes, 1 who seems to have been most successful in 

 applying the principles of Edward Forbes in the distribution of the 

 British Fauna and Flora to those of Australia and New Guinea. 



It is interesting to note that Jukes, while convinced that the northeast 



1 Voyage of the " Fly," Vol. I. p. .°.47. Jukes writes : " It follows that, during 

 the early part of the period of their formation, Torres Strait, and the shoal Beaa on 

 eaeli side of it, were dry land, and Australia connected to New Guinea. This would 

 explain, perhaps, the fact of the marsupial type of animals being common to both, 

 though the genera and species are different. It would explain also the difference 

 in the assemblage of shells, etc , on the northern and southern sides of Torres 

 Strait mentioned before, page 220, as each group would spread into the newly 

 formed sea from the nearest adjacent shores, the Molucca group coming from the 

 north, and the Australian from the south. The existing vegetation of the two 

 countries would seem to have originated, or at least to have spread over their 

 opposite shores since their separation." 



