PART II. CHAPTER XXI. 



253 



Mountain Limestone. 



CHAPTER XXI. 



CARBONIFEROUS GROUP Continued, and old red sandstone. 



Corals and shells of the Mountain limestone — Hot climate of the Carboniferous 

 period inferred from the marine fossils of the Mountain limestone and the plants 

 of the Coal — Origin of the Coal-strata — Contemporaneous freshwater and marine 

 deposits — Modern analogy of strata now in progress in and around New Zealand 

 — Vertical and oblique position of fossil trees in the Coal — How enveloped — 

 How far they prove a rapid rate of deposition — Old Red sandstone — its subdi- 

 visions — its fossil shells and fish. 



Carbonifeiious or Mountain limestone. — We have already 

 seen that this rock lies sometimes entirely beneath the Coal- 

 measures, while in other districts, it alternates with the shales 

 and sandstone of the Coal. In both cases it is destitute of land 

 plants, and usually charged with corals, which are often of large 

 size ; and several species belong to the lamelliferous class of La- 

 marck, which enter largely into the structure of coral reefs now 

 growing. There are also a great number of Crinoidea, and a few 

 Echinida, associated with the zoophytes above mentioned. The 

 Brachiopoda constitute a large proportion of the MoUusca, many 

 species being referable to two extinct genera, Spirifer (or Spiri- 

 fera) (Fig. 264.) and Producta (Fig. 265.). There are also 



Fig-. 264. Fig. 265. 



Spirifera glabra. Sow.* Producta Martini, Sow.f 



Mountain hmestone. Mountain limestone. 



many univalve and bivalve shells of existing genera in the 

 Mountain limestone, such as Turritella, Buccinum, Patella-, Iso- 

 cardia, Nucula, and Pecten.ij: But the Cephalopoda depart, in 



* Phillips, Geol. of Yorksh. pi. 10. fig, 11. 



t Ibid., pi. 8. fig. 19. i Ibid., vol. ii. p. 208. 



YV 



