Subclass ODOWrOHOLC~a~

Introduct ion. Birds are perhaps the most successful group of living vertebrates, and yet their fossil record is by far the poorest. The identification of birds from isolated skeletal fragments poses incredible difficulties and it is therefore not surprising that specialists in this subject are extremely thin on the ground. At the same time, as James Fisher points out, "nature can scarcely ever have given us a proper sample of the avifauna of any time at any horizon; the favoured candidates were nearly always the bigger birds--the marsh-birds, water-birds, shore-birds and continental-shelf sea-birds, and the birds of prey that preyed upon them". These problems not-withstanding, Fisher has produced a remarkably complete picture of the fossil record of birds. It is to be hoped that as a result of his two contributions to this volume, this history will in future receive the prominence it clearly merits. [L.B.H.T.