106 Mr. H. Seeley on Cambridge Geology : — 



supply of very salt water being obtained : it is just possible that 

 this rock may be that of St. Neots. There can be no doubt 

 that it holds a place at least that depth below the rock of St. Ives ; 

 for the prevailing fossils at St. Neots {Ammonites spinosus, 

 Duncani, and athletus), which occur almost to the exclusion of 

 other forms, will, with Ammonites coronatus, indicate a bed much 

 lower than that of St. Ives, which has Ammonites cordatus, 

 Lamberti, Eugenii, &c, as most common. A considerable thick- 

 ness of strata is probably represented by this change of life in 

 time. Therefore, notwithstanding the circumstance that Prof. 

 Buckman has given the Ammonites Duncani and athletus (St. 

 Neots fossils) as occurring in the same highest bed of clay with 

 Ammonites Marice and Goliathus (St. Ives fossils), it will be readily 

 granted that the St. Neots rock is lower than that of St. Ives; 

 and this being so, it cannot but happen that it dips to the east, 

 passing under Elsworth ; and therefore, if persistent, it ought to 

 occur that the St. Ives rock, by a synclinal, should again crop 

 out somewhere S.W. of St. Ives, while both it and the Elsworth 

 rock should occur between Tetworth and St. Neots. Though I 

 have gone over the whole of this country with some minuteness, 

 it must be reserved for a future paper to say whether they are 

 to be seen or not. But the whole of Huntingdonshire is much 

 obscured by gravel ; so that, in the absence of brick-yard evidence 

 or wells, the chances of detecting them would be slight. 



Such, then, so far as is yet observed, is the succession of clays 

 and stone bands in the east of Huntingdonshire; but, from 

 observations made in Bedfordshire, there appears to be a great 

 thickness of clay beneath the lowest zone here seen ; and there- 

 fore it would be premature to conclude that the St. Neots rock 

 is identical with the Kelloway rock, which may yet be found 

 lower down. This being so, the Elsworth and other rocks can- 

 not but be regarded as strata high up in the Oxford Clay, and 

 probably of similar importance with that occurring near its 

 supposed base — conclusions which, it will presently be seen, are 

 also indicated by the fossils. 



Facts of no less interest than the succession of rocks are pre- 

 sented by the succession of the clay, which by them is separated 

 into well-marked subdivisions, each distinguished by a peculiar 

 assemblage of fossils. But not only do the organic remains 

 differ, but as the series of strata is ascended a gradual transition 

 is observed from those forms characterizing lower beds to those 

 occurring higher up, until at last some of the peculiar fossils of 

 the Kimmeridge Clay are found blended with those of the Oxford 

 Clay ; and further on, the true Kimmeridge Clay itself is met 

 with, as at Cottenham. In the absence of the Coral Rag, this 

 great succession has the appearance of one deposit, admitting, 



