42.8 J. ZT: WILSON. AND J, P. HIth. 
It is not, however, the object of the writers to attempt to 
give any comprehensive sketch of the evolution of the problems 
met with in such a study. Nor do they profess to supply any- 
thing lke a complete and adequate discussion, even of the 
present position of these problems. Their aim has from the 
outset been a much more limited one, and they feel absolved 
from making any such attempt all the more that general 
literary surveys of the kind referred to, along with sufficient 
bibliographical data, have been published comparatively re- 
cently by more than one distinguished authority in this 
department of science. Special reference may here be made 
to the address by Professor H. F. Osborn at the American 
Association in August, 1893, specially important from the 
palzontological side, to the masterly résume given by 
Professor Gustav Schwalbe in an address to the “ Ana- 
tomische Gesellschaft” at Strassburg in May, 1894; to 
the brief but lucid and interesting account by Mr. M. F. 
Woodward in ‘Science Progress’ for July, 18945; and, lastly, 
to that given by Professor W. Leche in his recent important 
monograph on “ mammalian tooth-development in the ‘ Bib- 
liotheca Zoologica,’ 1894-5. 
But although in the following pages no effort is made after 
historical completeness, abundant reference must necessarily 
be made to the various phases of scientific opinion upon the 
most important dentitional questions, and we trust that our 
statement of these questions will be found to be not only accu- 
rate, but sufficiently detailed for the purposes of discussion. 
In spite of the substantial enlargement of our knowledge of 
the mammalian dentition attained of late years, it must be 
admitted that no final settlement of some of the more im- 
portant issues has yet been arrived at. On the contrary, 
certain of the more novel phenomena recently brought to light 
have so far served rather to complicate than to simplify the 
problems involved. 
No mammalian order has called forth more discussion in 
respect of its tooth equipment than the Marsupialia. Pri- 
marily, no doubt, this is owing to the inherent peculiarities of 
