E. T. Newton — On Ammonifes Juremis. 493 



worn. But this is of small importance compared with the fact that 

 fresh sand is being continually introduced by them to the rounding 

 action of the waves. 



Nearly all castings are formed on a surface of sand which is in^ 

 clined towards the sea. At the first touch of the water, a casting 

 sinks down and swells out at the base, and more of the casting 

 flows down the slope than up it. This flowing was especially 

 marked at one spot on the Holy Island Sands, where the beach was 

 slightly inclined and the surface discoloured by mud. The castings 

 formed on it were composed of clean sand, and had evidently been 

 surrounded by one or several waves as the tide went down. We 

 cannot always be certain that the summit of a casting was originally 

 above its centre, but in every one by far the greater part of the 

 spread-out base lay below the highest point of the casting. In some 

 cases, the castings had entirely lost their vermiibrm appearance, and 

 were simply long low mounds, the longer axes pointing down the 

 slope. In others, they had flowed so much that they could only be 

 distinguished by their different colour from the surrounding sand. 



V. — Note on the Occurrence of Ammonites jurensis in the 

 Ironstone of the Northampton Sands in the Neighbourhood 

 OF Northampton. 



By E. T. Newton, F.G.S. 



("CONSIDERABLE doubt having been expressed with regard to 

 J the occurrence of the zone of Ammonites jurensis in the neigh- 

 bourhood of Northampton, much interest attaches to the discovery, 

 by Mr. T. Jesson of Great Houghton, of the typical Ammonite in 

 some abundance in this area. It is perhaps remarkable that there 

 should have been any doubt about the matter, seeing that in Samuel 

 Sharp's earlier paper ^ Am. jurensis was recorded among the fossils 

 from Duston, and this should have stimulated further search when 

 the doubt arose which seems to have caused this species to be 

 omitted from the later paper by the same author,^ in which some 

 palseontological errors of the earlier paper were said to be corrected. 

 This omission led subsequent writers to think that Am. jurensis did 

 not occur in the neighbourhood, and, indeed, it does not appear to 

 have been met with by other workers in the district until the present 

 discovery b}' Mr. Jesson. 



In 1874 Mr. Sharp conducted an excursion of the Geologists' 

 Association to Northampton, and in the report of that excursion 

 Mr. W. H. Hudleston ^ notices the section of the "ironstone series 

 of the ' Northampton Sand ' " at Duston Quarries, but does not 

 mention Am. jurensis as being among the fossils found. 



Mr. Beeby Thompson, in his paper on the " Upper Lias of 

 Northamptonshire," ^ maintains that the Am. jurensis zone is repre- 

 sented in the clayey series beneath the Northampton Ironstone, by 

 his " Upper Leda-ovum beds," although the characteristic Ammonite 



1 Q J.G.S. vol. xxvi. p. 354, 1870. ^ Q.J.G.S. vol. xsix. p. 296, 1873. 



^ Record of Excursions, London, 1S91, p. 452. 



* Journ. Northamptonshire Nat. Hist. Soc. vol. v. p. 54, 1888. 



