CARBONIFEROUS LIMESTONE, TITTERSTONE CLEE. 



119 



grey and blue hard encrinital limestone. In the central quarries (Heath's, Navers, &c.) the calca- 

 reous shales overlying the cropstone, are of red, green, and purple colours, with some calcareous 

 nodules and subordinate bands of limestone, called Tilestones, Rombo, &c. The Rombo, about 

 three feet thick at the Navers quarry, lies about fourteen feet above the Cropstone, the inter- 

 mediate beds consisting of yellow argillaceous marl, and black shivery shale, inclosing thin courses 

 of impure limestone. The great limestone is called the TVhitestone from its colour, and also the 

 Bottom Rock from its usual position. The aggregate thickness of the limestone strata varies 

 from fifteen to fifty-four feet. In some parts the beds are of fine oolitic structure, similar to the rock 

 at Oreton described in the following page (Clee Hill marble). The best beds, whether in a highly 

 crystalline state and chiefly made up of encrinital stems and shells, or having the oolitic structure, 

 are so free from earthy matter, that they are very superior in quality to the argillaceous limestones of 

 the underlying and adjoining Old Red and Silurian Systems. The variegated red, green, yellow, 

 and blue colours of some of the overlying shales, and the pure oolitic structure of some of the beds 

 are the most marked mineral distinctions of this limestone. 



The organic remains found here are common to the carboniferous limestone of other 

 districts, and among them may be enumerated — 



Spirifer distans. M. C. t. 494. fig. 3. 



octoplicatus. M. C. t. 562. figs. 2, 3 and 4. 



Productus Martini. M. C. t. 318. figs. 2, 3 and 4. 

 Spirifer bisulcatus. M. C. t. 494. figs. 1 and 2. 



cuspidatus. M. C. t. 120. 



with several other species of Spirifer and Crinoidea in abundance. A remarkable Ichthyodorulite, or fin-bone 

 of a fish, was also found in this limestone at Gorstley Rough, by the Rev. T. T. Lewis, which Mr. Agassiz has 

 called Ctenacanthus tenuistriatus 1 . 



The escarpment of this limestone affords an instructive example of the manner in 

 which the strata supporting the overlying coal-field, have been fashioned into the margin 

 of a basin, and made to assume their present tortuous outline. The zigzag form, as 

 expressed upon the map, is the result of a number of dislocations, by which the lime- 

 stone has been thrown at one point into a vertical position, and at others into angles of 

 various inclination accompanied with frequent divergences in the strike of the beds. For 

 example, each gulley between the mouth of the Cornbrook level, and the promontory of 

 Know! hill, marks the line of a separate transverse fault, and at every one of these breaks 

 the limestone is moved out " en echellon," so as to occupy a succession of steps at 

 various distances from the coal-field; the strike or direction of each mass being different. 

 Thus at the eastern end of the zone, the strike is east and west, then follow sundry de- 

 viations from that direction in the intermediate ledges ; and when we reach what may 

 be termed the great mass of limestone, extending from the " Grove " to the " Ashes," 

 the beds are thrown round at right angles to their former direction. Again they are 

 twisted back to an east and west strike, and by a number of faults and snaps, are sub- 

 sequently carried into the recesses of Gorstley Rough, beyond which place the cal- 

 careous system, as has been shown, thins out and disappears. Besides these disloca- 

 tions there are numberless minor faults. At the "Ashes" there is one which proves 



1 This specimen is in the Musuem of the Yorkshire Philosophical Society. 



p 2 



