1 82 Passage of Species. 



remarkable manner the same lithological character, 

 showing evidence of deposition in shallow water. It is 

 partly formed of pale marly limestones and clays, pass- 

 ing in places into shelly, and occasionally oolitic, build- 

 ing-stones. When partly decomposed near the surface, 

 it assumes a rubbly character, and forms a fertile soil, 

 whence its agricultural name of Cornbrash, the word 

 brash being an old word expressive of this loose rubbly 

 character. 



The Cornbrash is generally very fossi lifer ous, the 

 general assemblage of genera of Echinoderms, corals, 

 Cephalopoda, Brachiopoda, Lamellibranchiata, &c. being 

 much the same as in the Great and Inferior Oolites. 

 So much, indeed, is this the case, that of the forms found 

 in the Great Oolite, 1 00 species pass into the Cornbrash, 

 while of those in the Inferior Oolite, 89 species pass up 

 into the same formation. 



This community of forms is very important, showing 

 as it does, that if some of the Inferior Oolite species 

 are absent in the Fuller's Earth and Great Oolite, they 

 must, nevertheless, during the deposition of these strata, 

 nave lived elsewhere, and returned in a later time, that 

 of the Cornbrash, to inhabit the same area when a con- 

 genial set of marine conditions ensued, thus establish- 

 ing a strong and direct succession of life through the 

 whole of these formations which together, in the 

 language of the day, form the Lower Oolite. In fact, 

 this division of these strata into formations, is in great 

 part lithological, and the difference of faunas in them 

 was dependent on changes of conditions of depth &c. 

 in a sea, where limestone, sands, or clays were being 

 deposited. The four so-called Oolitic formations already 

 described, may in truth be spoken of as one, there 

 being not much more difference between their fossils, 



