3l6 JURASSIC. 



seams made up of the shells of small oysters.^ Oolitic structure is 

 seldom developed. The Great Oolite Limestone occurs in Lincoln- 

 shire and the northern part of Northamptonshire. 



Among the fossils are Ncmtilus suhtruncatus, Natica iextata, Ostrca 

 snhrugulosa, O. Soiverbyi, Homomya gibbosa, Ceromya coricentrica, 

 Modiola imhricata, M. cuneata, Myacitcs crassiuscuhis, Pholadoinya 

 lyrata, Pccten annulatus, Terebrahda maxiUafa, Rhynchonella co7icinna, 

 Clypcus MilUcri, Acrosalenia hemicidayoidcs, Isastrcva, also bones of 

 Cetcosaunis, and some Fish-remains, Hybodus, Pycnodus, etc. The 

 compact limestones are sparingly fossiliferous, but the intervening 

 shaly or marly beds afford a number of species, many of which 

 have been obtained at Tadmarton near Banbury.^ 



The Great Oolite Limestone, which attains a thickness of about 

 twenty-five feet, is a continuation of the Upper Zone of the Great 

 Oolite, and perhaps in part of the Forest Marble. It extends from 

 Towcester, over Salcey Forest, to Northampton. (See Fig. 46,) 

 Fossils have been obtained at Chadlington Down, near Chipping 

 Norton, and at the Fox quarry, near North Ashton, by Mr. T. 

 Beesley and Mr. E. A. Walford. 



The limestone beds (White Limestone) are worked for building-purposes, 

 road-metal, and lime-burning, at Holcot, Kettering, Higham Ferrers (Stanwick 

 Ragstone), Kingthorpe, etc. At Blisworth, where the limestone is quarried, one 

 of the beds is called Pendle. At Stamford both Great Oolite and Lincolnshire 

 Limestone occur. 



At Alwalton, near Peterborough, shelly flag-stone, which takes a good polish, 

 was formerly quarried. It was termed the Alwalton (or Allerton) Marble. 

 Flaggy beds occur also at Castor, etc. These beds have been regarded as Poorest 

 Marble, and very likely they do represent it. Many of the pilasters in Peterborough 

 Cathedral are composed of the Alwalton Marble. 



Great Oolite Clay. 



This clay, termed Blisworth Clay by Mr. Sharp, ^ and Great 

 Oolite Clay by Prof. Judd, occurs at the top of the Great Oolite 

 Series in Northamptonshire, resting on the Great Oolite Lime- 

 stone. In thickness it varies from two to twenty feet, and it 

 comprises a series of variegated, blue, green, yellow, and purplish 

 clays, often containing bands of irregular white or pale-green 

 calcareous concretions, and sometimes septaria. It contains Ostrca 

 subnigulosa, O. Soiverbyi, Plaainopsis socialis, etc. In part the beds 

 seem to be of estuarine character.* They may be seen near 

 Northampton, Oundle and Wansford. (See Fig. 46.) 



In the north-western part of Lincolnshire the Rev. J. E. Cross 

 has described beds of greenish clay about forty feet in thickness 

 underlying the Cornbrash and resting upon the Lincolnshire Lime- 



^ Geology of Rutland, etc., pp. 186, 201 ; S. Sharp, Q. J. xxvi. 354. 



2 T. Beesley, G. Mag. 1872, p. 279. 



3 Q. J. xxvi. 380. 



* Judd, Geol. Rutland, etc., p. 186. 



