al INTRODUCTION. 
also includes the little that is known of the geological history 
of the Monotremes, and likewise takes cognisance of a remark- 
able extinct group believed to have some affinity with the 
latter. In a work of the present nature it would, however, 
obviously be inadvisable to treat of the fossil forms in the 
detail with which their recent allies are described, and, accord- 
ingly, nothing more than a general sketch has been attempted. 
In marked contrast to the fulness of our knowledge of the 
Marsupials and Monotremes from the point of view of the 
systematist, is our deficiency with regard to their habits and 
mode of life, this being especially the case in respect to the 
breeding-habits of the Monotremata. It is not to the credit 
of the present generation that the working zoologist has for the 
most part to rely for his knowledge of the habits of the greater 
number of Marsupials upon observations—admirable enough 
in their way—published many years ago, and the Author 
cannot but hope that the appearance of the present little 
volume may act as a stimulus to those having the opportu- 
nities of increasing our knowledge on this subject, information 
being most specially desirable with regard to the mode of life 
of the smaller members of the group. 
R LYDEKKER. 
