Vol. 69.] DERIVED CEPHALOPODA OF THE HOLDERNESS DRIFT. 169 



10. The Derived Cephalopoda of the Holderness Drift. By 

 Chaeles Thompson, B.Sc. (Communicated by G. W. Lajipllgh, 

 F.E.S., F.G.S. Eead January 22nd, 1913.) 



Contexts. 



Paste 



I. Introduction 169 



II. The Liassic Ammonites, etc. from the Drift, and 



their Matrices 170 



III. Oolitic and Kimeridgian Cephalopoda from the 



Drift 177 



IV. Lower Cretaceous Cephalopoda 177 



V. Upper Cretaceous Cephalopoda 178 



VI. Summary and Conclusions 178 



VII. Lists of Derived Cephalopoda found in the Glacial 



Drift of Holderness 180 



I. Introduction. 



For a long time it has been common knowledge among geologists 

 that the Drift of Holderness, and of the Yorkshire coast generally, 

 yields specimens of Jurassic cephalopoda, and at one time these 

 specimens were assiduously collected. 



Early in the last century, Phillips, in his classic ' Illustrations 

 of the Geology of Yorkshire,' 1 stated that fully three-fourths of 

 the then known species of the fossils of the Lias could be found 

 in the ' Diluvium.' Again, Simpson and J. F. Blake, in their 

 respective writings, mention certain fossils as being more 

 abundant in the Drift of Holderness than in the known expo- 

 sures of the Lias. 



Since those authors wrote, the remanie fossils have been 

 ignored until recently. There are now, however, two large col- 

 lections of ammonites from the Boulder-Clay cliff's themselves, and 

 also from the beach-stones derived presumably from the same clay. 

 The one has been made by Mr. William Morfitt of Atwick, the 

 other by myself and my colleague, Mr. A. H. Denham, of Hymers 

 College, Hull. 



These two collections, along with other smaller ones, show that 

 Phillips almost certainly understated the proportion of known 

 forms obtainable from the Drift. It is more probable that prac- 

 tically every species of the multiform Liassic ammonites known 

 from Yorkshire exposures has also been found, or can be found, in 

 the Drift. 



Beside this stands the important fact that in the clay itself and 

 in the beach-stones there have now been found many fossil cephalo- 

 pods which, so far, have never been obtained, or at least recorded as 

 obtained, in situ in the Yorkshire Lias. The Oolitic and Cretaceous 

 forms are, however, less fully represented, though the Speeton 

 1 ' Pt. 1— the Yorkshire Coast ' 1829, pp. 176-77. 



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