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: Prof S.K. Donovan 

 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 theySpring 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: 



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 months for the UK, and 9 months for the rest of the world. 



WJrWLwr abbreviation: Bull. nat. Hist. Mus. Land. (Geol.) 

 © The Natural History Museum, 1999 



Geology Series 

 ISSN 0968-0462 Vol. 55, No. 2, pp. 47-137 



The Natural History Museum 



Cromwell Road 



London SW7 5BD Issued 25 November 1999 



Typeset by Ann Buchan (Typesetters), Middlesex 



Printed in Great Britain by Henry Ling Ltd, at the Dorset Press, Dorchester, Dorset 



