ANNIVEJRSARr ADDKESS OP THE PRESIDENT. 85 



The time assigned to the union is the latter part of the Secondary 

 era. Here it is necessary to remark that unless the two areas 

 remained united in the latter half of the Cretaceous period, Dico- 

 tyledonous Angiospermous plants, which form the great majority of 

 the forms common to New Zealand and Australia, must have existed 

 in the Australian area before there is any evidence of their having 

 appeared in the northern hemisphere. The essential point is, 

 that Australia and ITew Zealand are now divided by a broad 

 expanse of sea, between 1000 and 2000 fathoms in depth. 



2. The Solomon Islands. — The next case to be mentioned is very 

 simple, and is a rather curious illustration of the importance 

 of biological evidence. I have already noticed the interesting 

 account of the geology of the Solomon Islands given by Dr. Guppy, 

 and his discovery in those islands of deep-sea deposits. He infers, 

 on what appears at first sight good geological evidence, that the 

 region has undergone upheaval of not less than 12,000 feet in Post- 

 tertiarj^ times. The Solomon Islands, with New Britain and New 

 Ireland, are represented on the ' Challenger ' chart as connected 

 with New Guinea by a bank not exceeding 500 fathoms in depth, 

 and they are said by Dr. Guppy to be separated from each other by 

 channels about 400 fathoms deep*. 



Now the fauna of the Solomon Islands comprises mammals, 

 snakes, and batrachians in considerable numbers. As, in the seas 

 around New Guinea, floating wood washed down by rivers is said 

 to occur to an extent rarely met with in other parts of the world, 

 the occurrence of the Solomon Island mammals might perhaps be 

 accounted for, without supposing the islands to have been united to 

 New Guinea. The forms t represented comprise, besides bats, 

 several species of Mus, a genus that appears occasionally, by some 

 means or other, to be able to traverse arms of the sea, and one kind 

 of Plialanger or Ouscus, an arboreal marsupial. The same species 

 of Plialanger is found in New Britain and New Ireland, and an 

 allied variety, not specifically distinguished, occurs in New Guinea, 

 Ceram, Bourn, and Amboyna. The Phalanger also extends to San 

 Cristoval, the most eastern of the Solomon Islands, a matter of some 

 interest, as will be shown presently. 



The x^resence of the reptiles and batrachia is not, however, to be 



* I am indebted to Captain Wharton for the information that no accurate 

 poundings are recorded. 



t Thomas, P. Z. S. 1887, p. 320, 1888, pp. 470-483. 



