314 



OOLITIC GEOUP 

 Fig. 384. 



[Ch. XX. 



Pterophyllum comptum. Syn. Cycadites comptus. 

 Upper sandstone and shale, Gristhorpe, near Scarborough. 



Tisc. 385. 



Hemitelites Br&icnii, Goepp. 

 Syn. PMebopteris contigua, Lind. & Hutt. 



Upper carbonaceous strata, Lower Oolite, Gristhorpe, Yorkshire. 



At Brora, in Sutberlandsbire, a coal formation, probably coeval with 

 the above, or belonging to some of tbe lower divisions of the Oolitic 

 period, has been mined extensively for a century or more. It affords the 

 tbickest stratum of pure vegetable matter hitherto detected in any sec- 

 ondary rock in England. One seam of coal of good quality bas been 

 worked 31 feet tbick, and there are several feet more of pyritous coal 

 resting upon it. 



Fuller's Earth (h, Tab. p. 291). — Between tbe Great 

 and Inferior Oolite, near Bath, an argillaceous deposit, 

 called " tbe fuller's earth," occurs ; but it is wanting in 

 tbe north of England. It abounds in the small oyster 

 represented in fig. 386. 



Inferior Oolite. — This formation consists of a calcare- 

 ous freestone, usually of small thickness, which sometimes 

 rests upon, or is replaced by, yellow sands, called tbe sands of tbe Inferior 

 Oolite. These last, in tbeir turn, repose upon tbe lias in tbe soutb and 

 west of England. Among tbe characteristic sbells of the Inferior Oolite, 

 I may instance Terebratula fimbria (fig. 38V), Rhynchonella spinosa 

 (fig. 388), and Pholadomya fidicula (fig. 389). The extinct genus 

 Pleurotomaria is also a form very common in tbis division as well as in 

 the Oolitic system generally. It resembles the Trochus in form, but is 



Ostrea acuminata. 

 Fuller's Earth. 



