Vol. 52.] IN YORKSHIRE AND LINCOLNSHIRE. 201 



few miles farther south, the Spilsby Sandstone is capped by this 

 band of oolitic, clayey, and sometimes slightly gritty ironstone 

 crowded with fossils, which is about 15 feet thick in the brow of the 

 hill south of Nettleton, where it has been mined, but probably not 

 elsewhere so thick. In this locality both the upward and the down- 

 ward limits of the ironstone-rock are fairly definite, but it is usually 

 overlain by a clayey band crowded with oolitic ferruginous grains 

 which appears to contain the fauna of the ironstone along with a 

 few newer forms. Northward it seems to thin out and disappear 

 shortly before the accompanying strata are overlapped by the Upper 

 Cretaceous rocks near Clixby. In the opposite direction it is still 

 a well-marked feature in the series 12 miles south of Nettleton, 

 the railway-cutting at Benni worth Haven, near Donnington, de- 

 scribed by Mr. H. Keeping, 1 revealing 9 feet of this rock, while 

 its original thickness may have been more than this ; but farther 

 south it appears to merge more or less into a clayey deposit. At 

 the southern termination of the Wolds it is represented by irregular 

 gritty ferruginous bauds with deep partings of sandy clay. East 

 of the Wolds it was recognized in the borings at Willoughby and 

 Skegness, and in both localities was interstratified and mixed with 

 clay. 2 



By Prof. Judd and the officers of the Geological Survey the 

 Claxby Ironstone is classed with the Tealby Clay ; but the earlier 

 observers, Messrs. Dikes and Lee, were inclined to connect it with 

 the underlying sandstone, 3 and Mr. H. Keeping observes that its 

 fossils ' differ somewhat considerably from those of the clays and 

 limestone above ' (op. cit. p. 241). 



As in the Spilsby Sandstone, lamellibranchs are the most abundant 

 fossils. These are chiefly of the genera Exogyra, Trigonia, Pecteti 

 (including numerous individuals of the gigantic P. cinctus), 

 Cucullcea, Lima, Panopcea, etc. 4 Many of the species occur like- 

 wise in the underlying sandstone. Brachiopoda are also numerous, 

 especially in the Acre House section, where they seem to charac- 

 terize the clayey material immediately overlying the harder rock 

 (see section, p. 203). 



The cephalopoda are represented by both ammonites and belem- 

 nites, but while the latter are of common occurrence, the former 

 are rare and poorly preserved. All the belemnites that I have 

 been able to observe in place in the Ironstone, whether at Nettle ton 

 Hill, Donnington, or Hundleby, have belonged to the lateralis-groun 

 (including B. lateralis, Phill., B. russiensis, d'Orb., and B. sub- 



1 Quart,. Journ. Geol. Soc. vol. xxxviii. (1882) p. 243. 



2 A. J. Jukes-Browne, ibid. vol. xlix. (1893) pp. 467 & 472. 



3 Messrs Dikes and Lee's description of the deposit, is as follows : — 'A mass 

 of small, globular, shining grains, of a dark brown colour, cemented together by 

 ferruginous matter ; it occurs in the higher part of the bed [green sand and 

 sandstone] nearly at its junction with the grey stone; and, possibly, ought to 

 have been classed with it,' Mag. Nat. Hist, ser.2. vol. i. (1837) p. 505. 



4 Prof. Pavlow (op. cit.) has recently recognized among these Aucella Keyser- 

 lingi, Lahus., a form well known in Russia. 



