164 REPORT — 1869. 



"The irregular beds of Polyparia consist of nodules or masses of crys- 

 tallized carbonate of lime, which afford, invariably, evidences of the labours 

 of the Polypus ; and associated with them are othei's of earthy limestone, 

 which bear only partial proofs of an organic origin. The whole are con- 

 nected by a pale bluish or yellowish stiff clay. It happens frequently that 

 a bed is composed of one genus of Polyparia." 



In Yorkshire the Coralline Oolite is well developed, and several reefs are 

 found at Hackness, Ayton, Seamer, &c. John Leckenby, Esq., F.G.S., of 

 Scarborough, gives the following details (see Dr. Wright, op. cit.) : — • 



" In various parts of the district occupied by the Coralline Oolite around 

 Scarborough are found patches of coral-reef sometimes occupying an area 

 of fully an acre ; and although never attaining an altitude so high as the 

 beds on the inclined surfaces of which they rest, they are truly the uppermost 

 beds of the formation. 



" They are sometimes from 10 to 15 feet in thickness, and consist of a 

 series of layers of crystallized coral from 18 to 24 inches in thickness, of the 

 species Tliamnastrcea concinna, Goldf. (which is the T. micraston, Phillips), 

 each layer being separated by rubbly clay and mud, in all probability being 

 the decomposition of each successive reef. The rock is quarried to supply 

 material for repairing the roads of the district ; but it is by no meains so well 

 adapted for the purpose as the adjacent calcareous grit, which, at the cost of 

 a Httle additional labour, would furnish a material much more durable. The 

 crystalline coral-reef is quickly ground to powder, and its use affords less 

 satisfaction to the traveller than to the geologist, as the blocks which are 

 stored up for use along the sides of the road yield many a handsome specimen 

 to adorn his collection. 



" The largest deposit is near the village of Ayton : there are others not 

 quite so extensive; one near the village of Seamer, another close to the 

 hamlet of Irton, and others in the neighbourhood of Wykeham and Prompton 

 ■ — the intervening distances being about a mile in every case." 



Messrs. Leckenby and Cullen visited the coral-reefs of the Coralline Oolite 

 near Scarborough with Dr. Wright, who writes as foUows :■ — 



" One quarry, near Ayton, wliich may be considered as a type of the others, 

 consisted of masses of crystalline coralline limestone, the beds having an 

 irregular undulating appearance. The corals appear to have grown in areas 

 of depression of the coralline sea ; the rock consists of largo masses of highly 

 crystalline limestone, forming nodulated eminences and concave curves, in 

 beds of from 12 to 18 inches in thickness, having a stratum of yellowish clay 

 filling up the hollows, and forming a horizontal line again to the stratification ; 

 then follows another stratum of crystaUine limestone, which assumes the 

 same nodulated condition as the one below it, the siirface of the coral 

 masses, where exposed, showing that the whole is almost entirely composed 

 of a small-celled Astraa, Th/imnastnea concinna, Goldf., Micraston, Phillips, 

 in some altered condition ; the reef is exposed to about 10 feet in section, and 

 rests on another, forming the floor of the quarry, and which descends many 

 feet deeper ; the corals arc bored by GaatrocTuence, and numerous shells were 

 seen imbedded in the coral mass, which had nestled in the crannies of the 

 reef." 



Dr. Wright sums up with regard to the French, German, and British strata 

 of the Etage Corallieu as follows : — 



" From this general view of the geographical distribution of the Coralline 

 zone, it would appear that this formation was composed of a series of coral- 

 reefs in the Jurassic sea, which, during the period of their construction, occu- 



