PALEONTOLOGY. 



The above-mentioned organic remains stamp the beds 

 containing them as being of terrestrial, freshwater, or at 

 most estuarine origin ; but amongst the debris we notice 

 slabs and pieces of impure limestone which yield speci- 

 mens of more marine forms of life, such as Goniatites 

 Listeri and Aviculopecten papyraceus, and possibly a 

 closer view may disclose the presence of smaller organ- 

 isms, such as the minute annelid, Microconchus carbo- 

 narius. We subsequently ascertain that the fragments 

 disclosing those remains have come from the bed marked 

 limestone in the section on p. 212. 



Now, descending the pit, we explore some of the 

 main passages or gate-roads, under the guidance of 

 the foreman, or " butty-collier ;" in some places we 

 find the roof above us to be crowded with splendid 

 impressions of ferns and other plants, the shales im- 

 mediately above the coal being often extremely rich 

 in such remains ; and we thence obtain better and 

 more perfect specimens than we could at the mouth 

 of the pit, with the additional advantage of knowing 

 the precise horizon or band in which they occur. 



From the information thus obtained we learn that 

 frequent oscillations of level took place in the area 

 where these beds were deposited; for instance, the 

 shales above the third coal-seam mark a slight de- 

 pression of the low-lying land on which the vegetation 

 grew, and its temporary submergence under the waves 

 of the neighbouring lake or estuary; after a slight 

 upheaval which allowed the growth of the thin coal, 

 it again sank under the water and was covered up by 

 the overlying shales, the depression reaching its farthest 

 extent when the impure marine limestones were formed ; 



