EOCENE MARL OF COGQINS POINT. 451 



tion of this marl was given precisely as it now stands in pages 144, 

 145, of the latest edition. My still earlier discovery of and ob- 

 servations upon the peculiar character of the underlying bed of 

 gypseous or "green-sand" earth (which will be treated of subse- 

 quently), led me to observe the peculiarities of the eocene marl, 

 which being less distinctly marked, might otherwise have escaped 

 my notice. 



As stated above, it was not from any knowledge of geological 

 theories of successive formations, and different ages and periods, 

 of all which I was profoundly ignorant, that my opinion of the 

 peculiar character of this marl was influenced. But judging 

 solely from the more rotten and disintegrated state of the shells, 

 and their entire disappearance generally, even though their calca- 

 reous material remains and from the total difference of kind of 

 the few shells remaining whole, or of which the shape is distinctly 

 marked, from any others of the many shells then known to me in 

 any other marls, I very early formed the opinion that this bed was 

 one of the remains or ruins of a condition of the earth much more 

 ancient than that in which the ordinary marls had been formed. 

 I remember having stated this opinion to one of the earliest of the 

 several geologists who at different times visited my dwelling-place 

 and my marl excavations. This was the since notorious Feather- 

 stonhaugh, to whom I pointed out this curious and to me highly 

 interesting deposit, and directed his attention to the more modern 

 and very different (miocene) marl lying immediately upon and in 

 close contact with the mucli more ancient formation below. This 

 remarkable feature I also showed at a later time to Professor Wil- 

 liam B. Rogers, who was much struck with the fact, and attached 

 so much, importance to it, that he has referred to it in several of 

 his subsequent publications. , 



The most ready and certain mode of distinguishing eocene marl, 

 is by reference to some of the shells belonging to this kind, and 

 which are never found in miocene marls. There are many such ; 

 but the most common and well marked are the tyro following : 1st. 

 The cardita planicosta, a bivalve white shell, having numerous re- 

 gularly formed flat ridges running from the point at the hinge of 

 the valves to the circumference of the outer or opening parts, and 

 widening as the ridges extend both valves alike, and having out- 

 lines approaching to circular sometimes seen four inches across, 

 and the connected valves two inches through ; but generally of 

 much smaller and various sizes. 2d. The ostrea sellccformis, or sad- 

 dle oyster, a curiously and variously contorted gray and very hard 

 bivalve shell, the larger valve of which approaches the shape and 

 reversed curves of a saddle. This shell is sometimes found more 

 than five inches in length. Both of these shells are abundant, 

 especially the cardita planicosta, in this particular bed of eocene 



