] 20 KEV. J. E. CEOSS ON THE GEOLOGY OF N.W. LINCOLNSHIKE. 



A thick bed of blue marl (figs. 2 & 3, g) succeeds, 90 feet in depth, 

 its lower portion the home, probably, of Ammonites oxynotus ; but no 

 opening has been made of any importance in the lower portion of this 

 marl, and its contents are unknown. Since writing, I have found in it 

 a little A. Buxhii, Sow. Its upper portion is crossed by bands of chert 

 nodules, and has yielded Ammonites raricostatus, Taylori, and, 

 perhaps, the Polymorphus mixtus of Quenstedt. A little higher, 

 again, in the same, I find A. Loscombei, Oxynotus numismalis 

 (Quenst.), and Natrix rotundus (Quenst.), the last imbedded in the 

 nodules, the others chiefly in the clay; with these are a large 

 Pinna, Pholadomya ambigua of a huge size, GrypTicea Maccullochi, 

 and Belemnites paxillosus. A narrow ironstone-bed (figs. 2 & 3, /) 

 follows, consisting of a rocky band 4 feet thick, the slabs crowded 

 with Pectens of a good size. They resemble the shell which Phillips 

 figures, in his ' Geology of Yorkshire,' under the name of " sublcevis, 

 Young and Bird;" (on turning to "Young and Bird," however, I 

 think that for sublcevis we should read " subrufus "). Prom this 

 profusion of Pectens we have named the bed the Pecten-ironstone. 

 The Ammonites it contains are A. armatus and Henleyi, which suf- 

 ficiently define its place in the series. I must mention one other 

 of its fossils, a large Tancredia, which seems wholly new, and to 

 which I would give the name " liassica" 



"We now reach the border between the Lower and Middle Lias, 

 the latter represented by some 66 feet of blue clay (figs. 2 & 3, e), 

 containing, throughout, in the centres of cement nodules, the A. 

 maculatus (Capricornus of Schlotheim). 



A railway -cutting, called Santon cutting, drives right into this 

 clay ; but few fossils are to be gathered. It is capped by a narrow 

 bed of 18 inches (not marked in the sections), containing a confused 

 mass of broken Belemnites and other shells, together with many 

 coprolites and much pyrites, the whole of a bright green colour. 



The true Middle Lias (the zone of A. margaritatus and spi- 

 natus, which lies next above in the normal series, is reduced with 

 us to very slender proportions. The margaritatus-heds seem to be 

 wholly missing ; and we find only 8 or 9 feet in all between the 

 occurrence of A. maculatus and A. communis. This 8 feet is repre- 

 sented in the sections by the band marked d. "We call it the Ehyn- 

 c7ionella-hed, from the frequent occurrence in it of H. tetrahedra ; it 

 consists, as far as my knowledge goes, of a hard light-grey limestone, 

 weathering to brown, and seems to contain Ammonites spinatus 

 (Brug.) towards the lower part, and A. communis and serpentinus in 

 the upper. 



Above this, again, the Upper Lias is represented by a bed (marked 

 c in the sections) about 60 feet in thickness, but very little explored. 

 It seems to consist chiefly of a blue shale, with casts of Ammonites 

 of the falcifer type ; and I think it shows no trace of Upper-Lias 

 sands. 



And now we reach the summit of the middle escarpment in my 

 section, and leave the Lias for the Oolites. 



The great formation now called " Lincolnshire Limestone " (figs. 



