The Bulletin of The Natural History Museum (formerly: Bulletin of the British Museum 
(Natural History) ), instituted in 1949, is issued in four scientific series, Botany, 
Entomology, Geology (incorporating Mineralogy) and Zoology. 
The Geology Series is edited in the Museum’s Department of Palaeontology 
Keeper of Palaeontology: Dr L.R.M. Cocks 
Editor of Bulletin: Dr M.K. Howarth 
Assistant Editor: Mr C. Jones 
Papers in the Bulletin are primarily the results of research carried out on the unique and ever- 
growing collections of the Museum, both by the scientific staff and by specialists from elsewhere 
who make use of the Museum’s resources. Many of the papers are works of reference that will remain | 
indispensable for years to come. All papers submitted for publication are subjected to external peer review for | 
acceptance. 
A volume contains about 160 pages, made up by two numbers, published in the Spring and Autumn. 
Subscriptions may be placed for one or more of the series on an annual basis. Individual numbers and back 
numbers can be purchased and a Bulletin catalogue, by series, is available. Orders and enquiries should be 
sent to: 
Intercept Ltd. 
P.O. Box 716 | 
Andover | 
Hampshire SP10 1YG | 
Telephone: (01264) 334748 : 
Fax: (01264) 334058 
Claims for non-receipt of issues of the Bulletin will be met free of charge if received by the Publisher within 6 | 
months for the UK, and 9 months for the rest of the world. 
World List abbreviation: Bull. nat. Hist. Mus. Lond. (Geol.) 
© The Natural History Museum, 1997 
Geology Series 
ISSN 0968-0462 Vol. 53, No. 2, pp. 79-139 
The Natural History Museum 
Cromwell Road 
London SW7 5BD Issued 27 November 1997 
Typeset by Ann Buchan (Typesetters), Middlesex 
Printed in Great Britain by Henry Ling Ltd, at the Dorset Press, Dorchester, Dorset 
