375 



VI. GENERAL REMAEKS. 



It may now be gathered from the course of my examiBation of 

 the nature and contents of this stage of the Middle Lias, what was 

 to a considerable degree of approximation, its position petrograph- 

 ically, and also, the phase of organic life it has transmitted us. 



In estimating the former, that is, the natural position of these 

 beds, it was necessary to first make a precise and accurate 

 survey of all the lithological details. This having being done, 

 a careful comparison was next made between these data, and 

 recent similar submarine deposits. Recourse was had for this 

 piu'pose, to the hydrographical Tables of M. Delesse, that 

 form the second vol. of his admirable work, entitled " Lithologic 

 du Fond des Mers." * From the study of this valuable com- 

 pendium of actual observations, a work of immense labour, we 

 have been led to carefully form conclusions that may be depended 

 upon. Some of the inferences thus afforded, have been already 

 anticipated in my remarks under the special headings. Still, I 

 will now briefly sum up the obvious deductions drawn from our 

 preparatory work. The positions we arrived at are these : — 



1. The beds of the Spinatus Zone, were a marine deposit of 

 sub-littoral character. 



2. They were protected in a bay, cove, recess, or indentation 

 of the coast line of the liassic sea, for otherwise, had they been 

 entirely unprotected from the race of the tidal waves, they 

 would have contained no moUuscan remains ; as the unre- 

 strained force of the submarine currents, would have swept out 

 of them all traces of organic life. 



3. These beds were formed below the level of the lowest tides. 



4. The various fossils obtained from them shew us that their 

 true position was within tha,t littoral division known as the 

 Laminarian Zone, which was about 15 fathoms in depth. 



5. Judging from the nature and habits of the Mollusca of the 

 Zone, they must have inhabited a warm natural-history province. 



There yet remains an interesting inquiry, that which concerns 

 this Zone in its horizontal extent and direction. It is eitsy to 



* In M. Delesses work, the tabulated results of his extensive hydrographical 

 observations upon all oiu- chief littoral and open sea accumulations are given 

 with a suqirising completeness. 



