1868.] JUDD SPEETON CLAY. 219 



succession of the beds which compose it ; and, as this part of the 

 Yorkshire coast-section is greatly coniphcatcd by faults and contor- 

 tions, and much obscured by landslips and drift, I soon became con- 

 vinced that it was only by such detailed and systematic examination 

 that satisfactory conclusions wci-e to be arrived at. The fact that 

 the mining operations now pursued on an extensive scale at these 

 cliffs are rendering this imiqae section ^ery year more and more 

 obscure acted as a further incentive ; and I accordingly determined 

 on the execution of the following tasks : — 



1. A careful survey of the Speeton Cliffs, and the construction of 

 a map and section upon a very large scale, showing the various 

 landslips &c., with a view to arriving at the true succession of the beds. 

 The necessary basis for this work was opportunelj^ furnished by the 

 publication in 1862 of the beautiful 6-inch Ordnance Map of this 

 part of the Yorkshire coast. 



2. The collection of the fossils and drawing up accurate lists of 

 the contents of the several beds. The incompleteness of the various 

 collections of Spec ton fossils, the absence of notes on the specimens 

 in those collections, indicating from what portion of the section they 

 were obtained, and the large admixture of species not belonging to 

 the deposit at all rendered this task indispensable. 



3. The critical examination of the undoubted Speeton fossils, and 

 a comparison of them with the figures and descriptions contained in 

 the works of continental palaeontologists, and, where possible, with 

 authentic foreign specimens. The possession by the British Museum 

 of an extensive series of foreign j^eocomian fossils, from the collec- 

 tion of MM. Astier, Paul Mohr, and others, greatly facilitated this 

 part of my undertaking. 



II. Bibliography oe the Subject. 



The earliest notice of the Speeton Clay with which I am acquainted 

 is that of Young and Bird*, who in 1822 gave a very careful and 

 exact account of the physical character of these beds,, with figures 

 and descriptions of a few of the fossils. They ^called these strata 

 " the Upper Shale," but made no serious attempt at their corre- 

 lation. 



In 1826t Professor Sedgwick gave a detailed description of the 

 Speeton section (from observations made in 1821), and referred the 

 clays to the Kimmeridge, noticing, however, the peculiarity in the 

 fauna of their upper portion. 



In Phillips's ' Geology of Yorkshire 'J the beds are described under 

 the name of the Speeton Clay, a considerable number of the fossils 

 are figured, and the striking distinction between those from the 

 upper and lower part respectively clearly pointed out ; the former 

 were assigned to the Gault, the latter to the Kimmeridge Clay. 



^ Survey of Yorksliire Coast, 1st ed. (1822), 2nd ed. (1828). 

 t " On the classification of the strata which appear on the Yorkshire Coast," 

 Ann. of Philosophy, vol. xi. (182G) p. ^^t). 

 t Isted. (1829) p. 76. 



