1896. NOTES AND COMMENTS. 365 



marsupials, the most important anatomical distinction in the group 

 relates to the character of the incisor teeth of the lower jaw. One 

 great division is termed Diprotodont, because the median lower incisors 

 are enormously long, are horizontal in position, and dominate the 

 aspect of the front of the mouth. The other great group is described 

 as Polypvotodont. In these, as in existing carnivorous animals, the 

 large canines are the chief feature of the front of the lower jaw, while 

 the incisors between them are small and inconspicuous. A few years 

 ago it would have been asserted confidently that Diprotodont creatures, 

 living or extinct, were peculiar to Australia and the adjacent islands. 

 Recently, however, Senor Florentino Ameghino has described a 

 number of fossil Diprotodont creatures from the rocks of Patagonia. 

 The age of the geological strata in which these interesting fossils were 

 found is doubtful. Ameghino thinks that the beds are Middle Eocene. 

 Mr. Lydekker, who has examined the remains more recently, regards 

 them as much later, probably as Oligocene or Early Miocene. 



Here, however, is a link binding together Australia and South 

 America, and pointing vaguely towards a former land-connection 

 between the extremities of land in the Southern Hemisphere. Much 

 weight could not have been laid upon the existence of Polyprotodont 

 marsupials in Australia and in South America, because, not only do 

 these extend into North America, but fossils referred with consider- 

 able certainty to the Polyprotodonts occur throughout the Northern 

 Hemisphere. The Diprotodonts, however, living and fossil, are 

 known only in South America and the Australian region. It was 

 possible to argue, while only Ameghino's fossils were known, especially 

 if there were accepted his ascription to the Eocene Period of the 

 beds in which they were found, that Diprotodont fossils might yet be 

 found in the Northern Hemisphere, and that their occurrence in 

 Patagonia was no strong argument for the existence of a recent land- 

 connection between Australia and South America. Mr. Thomas' 

 new mammal, Ccenolestes obsairiis, recently obtained by a native hunter 

 in Bogota, and now in the British"" Museum, strengthens the case for 

 the land-connection enormously. For Mr. Thomas, in his careful 

 account of the characters presented by the skull, proves that it 

 belongs to the Epanorthidae, one of Ameghino's fossil Diprotodont 

 families. The Diprotodonts, living and fossil, therefore, so far as is 

 known, are confined to Australia and South America, and occur in 

 both these regions. 



Lime in Plant Chemistry. 



In the most recent issue of the Annals of Botany (vol. x., no. 37) 

 P. Groom gives an account of some experiments on the function 

 of calcium in plant chemistry. It is well-known that plants will not 

 thrive unless supplied with a small amount of calcium in their food ; 

 one of the symptoms of mal-nutrition when this element is absent 

 being the accumulation of starch in the tissues. 



