INTRODUCTION. 



Detailed accounts of three families only of English Cretaceous Lamellibranchs 

 have hitherto been given, namely, the Trigoniidse by Lycett, and the Nuculidae and 

 Nuculanidae by Gardner. Numerous species, however, belonging to various 

 families, were described and figured by J. and J. de C. Sowerby in the ' Mineral 

 Conchology,' and a few also by Parkinson in his ' Organic Remains of a Former 

 World.' A number of works, dealing primarily with the stratigraphy of the 

 Cretaceous beds, also contain descriptions and illustrations of Cretaceous Lamelli- 

 branchs from certain districts or from special horizons. One of the earliest of 

 these is ' The Fossils of the South Downs ; or, Illustrations of the Geology of 

 Sussex,' by Gideon Mantell (1822), in which a number of Lamellibranchs from the 

 Gault and Chalk of the south-east of England are described and figured ; but 

 unfortunately the figures are not very satisfactory, and in many cases the type- 

 specimens are now missing ; nevertheless, with the aid of other examples collected 

 from the same localities, it is usually possible to discover the characters of 

 Mantell's species. 



Another early work dealing with a special district is the ' Illustrations of the 

 Geology of Yorkshire,' by John Phillips (1829), in which a few Lamellibranchs 

 from the Speeton Clay are figured and others recorded. In ' An Outline of the 

 Geology of Norfolk,' by S. Woodward (1833), the more important species from the 

 Norwich Chalk are illustrated, but descriptions are not given. 



In Fitton's great memoir (1836) on ' The Strata between the Chalk and the 

 Oxford Oolite in the south-east of England,' many species of Lamellibranchs, 

 chiefly from Blackdown, are excellently figured and briefly described by J. de C. 

 Sowerby ; and most of the type-specimens are now preserved in the Bristol 

 Museum. An account of the more important Lamellibranchs from the Lower 

 Greensand of the Isle of Wight and of the Weald is given by Edward Forbes 

 (1845) in a paper entitled 'Catalogue of Lower Greensand Fossils in the Museum 

 of the Geological Society,' Part I. Most of the specimens therein described may 

 still be seen in the Society's Museum. 



Dealing with almost the same area as Mantell's work is the later publication of 



