130 rev. j. e. cross on the geology oe n.w. lincolnshire. 



Discussion. 



Mr. Ethertdge spoke as to the excellence of the paper, which 

 contained a most useful collection of facts. Two of the species of 

 Ammonites exhibited were rare, being new to Britain, and only 

 previously known in France and Germany, showing and confirming 

 the wide distribution in space of certain forms of this group. An 

 important feature in Mr. Cross's paper consisted in his determining 

 and correlating the zones of life in his area with those of the south 

 and west of England, especially as regards the lowest part of the 

 Lower Lias. The fixing the true position of the Frodingham iron- 

 stone and its associated fauna, fully establishing its place, thick- 

 ness, and value, and finally settling the point at issue as to its being 

 on the same horizon as the " Cleveland seam," is also of high 

 importance. 



Mr. Judd remarked on the interest attaching to this communica- 

 tion, not only as describing a district little known to geologists, but 

 also as furnishing us with evidence of very fine developments of geo- 

 logical horizons which elsewhere in this country are represented 

 only in a very imperfect manner, or not at all. 



Mr. J. F. Blake remarked that though the author had found no 

 exposure of beds between the angulatus-zone and the Keuper, they 

 probably existed, as they occurred both to the south and to the 

 north in Yorkshire, across the Humber. He agreed with the author 

 that the ironstone of Lincolnshire was on an entirely different level, 

 and was totally unrelated to that of Yorkshire, the true equivalent 

 of which, though here only 8 feet, was much thicker, though not 

 of any commercial value, across the Humber. The Pecten-be&s 

 mentioned were characteristic of the same zone in Yorkshire as in 

 Lincolnshire; but in the former county they contained no iron 

 except in the form of pyrites. The thinness of the upper beds 

 as contrasted with the thickness of the lower, showed a veritable 

 thinning-out of them, which was continued into Yorkshire, where 

 some of the fossiliferous bands of the Inferior Oolite described by 

 the author appear to be altogether wanting. 



Prof. Hughes said that he thought we should be careful not to 

 infer too hastily an interruption in the continuity of deposition from 

 the absence of certain fossils from the horizon at which they occur 

 in other sections. 



