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PREFACE

ONE of the greatest difficulties experienced by all who undertake a
work of this nature, not professing to be an exhaustive treatise

on the subject with which it deals, is to determine the amount
of detail desirable to be introduced to meet the requirements of
the ordinary student, without rendering it too bulky or costly
for general use. The experience of those who endeavour to profit
by the book can alone decide how far the authors have succeeded
in this respect.
It will be observed that in many instances certain
better-known or more interesting members of the class have been
described at considerable length, while it has been necessary to
treat others with much greater brevity.

With regard to the references to the literature of the various groups treated of, it has been the endeavour of the authors to make a selection of such memoirs and works as are likely to prove most valuable to the student for the amount of original information which they contain, and more especially of those giving full bibliographical data up to the time of their publication, the repetition of which has been considered unnecessary.

In a few instances new generic terms have been introduced to

replace some which were already occupied; these have been proposed by Mr. Lydekker, and should be quoted as his.

The work is based largely upon the article "Mammalia," together with forty shorter articles, written by the senior of the two authors for the ninth edition of the Encyclopædia Britannica. The account of the orders Rodentia, Insectivora, and Chiroptera contributed to the article "Mammalia" by Dr. G. E. Dobson, F.R.S., as well as the articles "Mole," "Shrew," and "Vampyre," by the same writer, the articles "Marmot," "Mouse," "Opossum," "Phalanger,' Rat," "Squirrel," "Stoat," "Vole," and others, by Mr. Oldfield Thomas, and likewise the article "Ape," by Dr. St. G. Mivart, F.R.S., have also been made use of to a greater or less extent. The best thanks of the authors are due to these three gentlemen for freely permitting the incorporation of their own work in the present volume.

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Mr. Lydekker undertook the task of arranging the various articles in their proper sequence, selecting from these such portions as seemed suitable, filling up the gaps, and adding new matter where necessary; a large amount of this new matter treating of the extinct forms, and also of the group Artiodactyla.

The subsequent revision, both before being sent to the printers, and also when passing through the press, has been made by both authors, who are thus jointly responsible for the whole work.

The illustrations are to a great extent those prepared for the various articles in the Encyclopædia, but many have been added -some drawn expressly for the work, and some borrowed from other publications. For most of the latter the authors take this opportunity of expressing their thanks to the Publication Com

mittee of the Zoological Society of London, as well as to the individual writers in whose works they first appeared.

The authors have further much pleasure in acknowledging the ready and obliging way in which Mr. Oldfield Thomas has, throughout the progress of the work, placed his extensive knowledge of the group of animals of which it treats at their disposal.

LONDON, March 1891.

CORRIGENDA.

Page 280, for Charopsis read Choropsis.

Page 292, for Chæropotamidæ and Chæropotamus read Choropotamidæ and Chœropotamus.

Page 590, for Pæcilogale read Poecilogale.