A. E. Trueman — The Lias of South Lincolnshire. 105 



spinatuvi 

 zone, 22 ft. Sin. 



1 



margaritatus 

 zone. 



ft. in. 



Ironstone with phosphatic nodules. Belemnites, 



Bhynchonella tetrahedra, Terehratida punctata, 



Cincta numismalis, Pleuromya costata, Pecten 



cBquivalvis, P. lumdaris ..... 



Light-grey shales with several thin phosphatic nodule 



beds . . . . . . . about 19 



Light-grey shales with Avialtheus sp. . . .10 



Ferruginous limestone with Pecten cequivalvis . . 10 

 Several phosphatic nodule beds .... 10 



Shale to base 30 



ftixn3iUvs?iV.lintoln. 



SrMitbriAcie .;\r U>\!La\n 



SjJinckl'um 



Fig. 3.— The Transition Bed and Middle Lias of Lincoln. 

 (P, level of phosphatic nodule beds.) 



Comparing the spinatum zone in. the above section with that at 

 Bracebridge it is seen, that the phosphatic nodule beds are not 

 contemporaneous (Fig. 3), and cannot be used for correlation. 

 J. H. Cooke/ after examining the section just described, concluded 

 that the ferruginous limestone which is taken to be near the upper 

 limit of the margaritatus zone was the Lincoln representative of the 

 Marlstone of other localities. This was shown to be erroneous by 

 the Rev. E. Nelson and Mr. H. Preston, Avho considered that the 

 upper rock bed was the Marlstone equivalent. It must be noted, 

 however, that only the lower part of this bed contains spinatum zone 

 fossils; the upper part lias numerous Dactyloids, a fact which was 

 apparently overlooked by previous writers. Thus the Lincoln 

 equivalent of the Marlstone ironstone of tlie south of the county is 

 a light-grey shale with abundant phosphatic nodules at varying 

 levels. 



1 J. H. Cooke, Geol. Mag., Dec. IV, Vol. IV, p. 253, 1897. 



