Ill 
EXPLANATORY. 
This Volume is printed in the Divisions enumerated on p. iv. 
The pagination of each Division is separate, arid is given at the 
left-hand top corner of the pages. The number and name of the 
Division is given as a heading on each left-hand page, 'the Registra- 
tion Numbers when of importance are given at the right-hand top 
corner of the right-hand pages. The date 1920 corresponding to 
the bulk of the literature indexed is given at the right-hand top 
corner of the left-hand page. 
In the Subject Index of each Division authors are quoted by name 
only. The full references will be found in the Title Section of the 
Division. 
The Literature indexed is mainly that of 1920 but includes entries 
for earlier years that have been received too late for inclusion in 
previous volumes. 
On account of the international situation, the Royal Society 
of London found itself unable to undertake at present any financial 
responsibility for any volumes of the International Catalogue 
subsequent to those of the Fourteenth Annual Issue. 
Under these circumstances the Zoological Society of London 
arranged to undertake the issue of the present volume, which is the 
fifty-seventh of the Zoological Record, and would have been N. Zoology 
of the Twentieth Annual Issue of the International Catalogue. Its 
preparation has been conducted as closely as possible on the model of 
the previous volumes prepared jointly by the International Catalogue 
and the Zoological Society. 
% 
It can now be purchased from the Zoological Society of London 
at the price of £2, either in the binding of the Zoological Record or 
in series with the International Catalogue. 
Volume 58, dealing with the Literature of 1921, is in preparation; 
it will be printed and issued if the replies to the explanatory circular 
issued to subscribers encourage the Society to undertake the heavy 
financial responsibility. 
