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



ft. in, 

 margaritatum Grey micaceous shale with ferruginous hmestone and 

 zone. thin bands of septaria. Amaltheus margaritatus, 



55 ft. 6 in. Amaltheus Itzvis, Cucullea miinsteri, Pectencalvus 25 



" Nodule Bed," a bed of ferruginous stone with small 



phosphatic nodules ...... 6 



Dark-blue shale, with scattered septaria. A. mar- 

 garitatus, Seguenziceras algovianum . . . 30 



The margaritahis zone at Grantham is much thicker than it is near 

 Lincoln and the ammonites of the Oistoceras sub-zone do not pass 

 into it. A curious feature of the margaritatus zone of Grantham is 

 the presence of a bed of phosphatic nodules. It has been suggested 

 that this bed is the equivalent of that seen near Lincoln/ but 

 evidently its horizon is very different. No exposure of the Transition 

 Bed has been examined in the Grantham neighboiirhood, but it may 

 be seen in the Caythorpe district, about eight miles to the norths 

 where the following section was measured near the railway bridge, 

 about a mile south of Caythorpe Church. 



ft. in. 

 tenuicostatum Paper shales with fish scales . . . • . 12 



sub-zone. 



? acutum Ferruginous sand . . . . . . . 4 



sub-zone. 



spinatum Oolitic ironstone . . . . . . .20 



zone. Blue-green ironstone weathering to reddish-yellow, 



fossils rare . . . . . . . . 12 



South of Grantham the junction of the Middle and Upper Lias may 

 again be seen near Harby, four hundred yards north-east of White 

 Lodge. 



ft. in. 



tenuicostatum Blue paper shales, Dactylioceras tenuicostatum, D. cf . 



sub-zone. semicelatuvi, Pseudolioceras sp. Fish scales . . 15 



Cream-coloured limestone with fish teeth and scales . 1 



'^acutum White limestone with many broken shells . . 2 



sub-zone. 

 spinatum Eed ironstone, with abundant Bhynchonella and 



zone. Terehratula . . . . . . . . 10 



At neither of these places, however, have any ammonites been 

 found in the beds which are taken to represent the acutum sub-zone. 

 It will also be noticed that the Transition lied thins out as it is 

 followed southwards through the county ; thus it is not indirect 

 continuation with that of the Midhmds. Probably there was 

 a slight uplift over the greater part of the country after the hemera 

 of spinatum, several shallow basins being formed, and during the 

 hemera of acutum sediments only accumulated in these restricted areas, 

 one of which was around Lincoln but only extended for a few miles 

 to the south. 



One of the most interesting fossils found in the Upper Lias of 

 Grantham is one which Mr. S. S. Biickman lias identified as 

 Harpoceratoides ovatum, Y. & B., indicating the pseudovatum sub- 

 zone, which liad not previously been proved to exist outside 



^ H. B. Woodward, Lias of England and Wales (Mem. Geol. Surv.), 1893, 

 p. 241. 



