During the autumn of 1930 I delivered for the Dental Board of the United Kingdom a course of four lectures on ‘Abnormal Conditions of the Teeth of Animals in their Relationship to Similar Conditions in Man’. These lectures were published in book form [Colyer, 1931]. In this volume I have given a fuller account of the subjects dealt with in those lectures, more especially the one on ‘Positional Variations of the Teeth’ and have added chapters on ‘Variations of the Teeth in Number and Shape’, ‘Abnormal Eruption and Growth of Teeth’ and on those interesting abnormalities usually classed as ‘Odontomes’. I trust that the facts recorded may be of some value to those interested in Comparative Dental Pathology.

I wish to record my thanks to the authorities of the Natural History Section of the British Museum for the facilities afforded me to examine the extensive collection of mammals’ skulls and for permission to photograph several of the specimens. I am also indebted to Major Powell-Cotton for placing at my disposal, for the purposes of study, the valuable collection of Apes and Monkeys in his museum at Quex Park and to Lord Rothschild for allowing me to examine his collection at Tring Park.