126 Geological Gleanings. 



level which have disconnected lands or seas formerly united. In 

 Silliman's Journal we find some facts of this kind, in relation to 

 Australia, New Guinea, and the Aru Islands, from a paper by 

 Mr. Wallace in the American Magazine of Natural History, 

 Shallow seas we are told, about 30 to 40 fathoms in depth, con- 

 nect all these islands. 



"But there is another circumstance still more strongly proving 

 this connexion : the great island of Aru, 80 miles in length from 

 north to south, is traversed by three winding channels of such 

 uniform |width and depth, though passing through an irregular, 

 undulating, rocky country, that they seem portions of true rivers, 



ough now occupied by salt water, and open at each end to the 

 entrance of the tides. The phenomenon is unique, and we can 

 account for their formation in no other way than by supposing 

 them to have been once true rivers, having their source in the 

 mountains of New Guinea, and reduced to their present condition 

 by the subsidence of the intervening land." 



Nearly one half of the Passerine birds of New Guinea hitherto 

 described are contained in the author's collections made in Aru, 

 and a number also of species in the other tribes. 



The author farther observes on the absence of the peculiar East 

 Indian types. " In the Peninsula of Malacca, Sumatra, Java, 

 Borneo and the Philippine Islands, the following families are 

 abundant in species and in individuals. They are everywhere 

 common birds. They are the Buceridce, Picidce, Bucconidcs, 

 Trogonidce, Metopidce, Eurylaimidce ; but not one species of all 

 these families are found in Aru, nor, with two tloubtful exceptions, 

 in New Guinea. The whole are also absent from Australia. To 

 complete our view of the subject, it is necessary also to consider 

 the Mammalia, which present peculiarities and deficiencies even 

 yet more striking. Not one species found in the great islands 

 westward inhabits Aru 'or New Guinea. With the exception only 

 of pigs and bats, not a genus, not a family, not even an order of 

 mammals is found in common. No Quadrumana, no Sciuridse, 

 no Carnivora, Rodentia, or Ungulata inhabit these depopulated 

 forests. With the two exceptions above mentioned, all the mam- 

 malia are Marsupials ; while in the great western islands there is 

 not a single marsupial ! A kangaroo inhabits Aru (and several 

 New Guinea), and this, with three or four species of Cuscus, two 

 or three little rat-like marsupials, a wild pig and several bats, are 

 all the mammalia I have been able either to obtain or hear of." 



