50 



HYATT ON THE TERTIARY SPECIES 



higher than the Old Pit, seems to show that the relative depth to which one may dig 

 in reaching the Jura does not count for much. The elevations which have taken 

 place, and which of course primarily affected the Jura clay also, make it impossible 

 to say that the strata rejjresented in a hole, six feet deep in one spot, may not 

 be of equal age with sti'ata resting on the Jura, in a hole fifteen or twenty feet deep. 

 The foldings of the formations and the broken aspect of the limestone layers above, 

 show that restricted local and vertical movements in the formations have taken place, 

 and that a general movement of the CJoister Ridge upwards has also taken place. 

 This last would account for the greater thickness of the formations as a whole as we go 

 outwards from the ridge, but not for the greater thickness of the same beds. If this is 

 a fact, such formations as a 1, 2, Sect. 5, are older than a 1, Sect. 6 ; and a 1, Sect. 4, 

 older than a 1, Sect. 5. 



The great uncertainty in this problem is the variability of adjacent beds, as in m-p, of 

 the two sections in the New Pit, or d, e,f, of the two sections in the East Pit. 



Of course, if the fossils followed each other in regularly arrangeable series, as 

 described by Dr. Hilgendorf, in a number of places, and throughout the entire series 

 of formations from the Jura clay to m inclusive, in every pit and excavation, there 

 could be no doubt, but, if they fail in a single section, it is fatal, provided the number 

 of exceptions found are sufficient to eliminate eri'ors of observation due to the accidental 

 intermixture of higher occurring species in lower formations ; and this appears to me to 

 be the real state of the case. 



The following section of 'Sandberger's is given in detail, because it was taken in 

 the East Pit, which is likely to vary exceedingly with farther exploration, and also 

 presents more difficulties than the others. 



My own Section 3, was not taken directly up the face of the cliff, but in two 

 connected parts of the cliff, and Section 2, from a hole in the centre of the pit. 



1 The correspondence here is much confused on account of the distribution of the shell-sand in pockets in the midst of the clay. 



