118 Mr. J. r. Walker in reply to Mr. Seeley on the 



XVII. — A Reply to Mr. H. G. Seeleifs Remarks on my Account 

 of the Phosphatic Deposit at Potfon, in Bedfordshire. By 

 J. F. Walker, B.A., F.C.P.S., F.C.S., F.G.S., Sidney Sussex 

 College, Cambridge. 



In April 1866 the Rev. P. B. Brodie wrote a paper on tlie phos- 

 phatic deposit near Potion, in Bedfordshire, and stated that the 

 fossils were derived from preexisting formations*. Having ob- 

 tained from this bed some additional fossils, especially remains 

 of Iguanudon, I wrote a short paper, supplementary to Mr. 

 Brodie^s, which was published in the Number of this Magazine 

 for July 1866. At this period the Woodwardian Museum con- 

 tained no fossils from this deposit ; but since then, through the 

 exertions of Mr. Keeping, who has the care of the Museum, it has 

 obtained a fine series of these fossils. In August of the same year 

 Mr. Seeley published a letter criticisiug the results arrived at 

 by Mr. Brodie and myself; but this fact does not appear from 

 his reference to that paper in the last Number of the * Annals,' 

 in which he would seem to intend to represent himself as the 

 person attacked, instead of the aggressor, in this matter. Mr. 

 Seeley stated in his letter that all the fossils appeared to him to 

 be " denizens of the old sea-bed where they abound -j" and this 

 is the chief point on which our views do not coincide. Mr. Seeley 

 says that the only mistake in his paper is the statement that 

 " the Gryphcea dilatata is perversely wanting.'' But I am not 

 surprised that Mr. Seeley obtained no specimens of this fossil, 

 as the work-people did not save the ferruginous shells until I 

 told them to do sof- I will now consider Mr. Seeley's criticisms 

 seriatim. 



I. Mr. Seeley objects to this deposit being called the Lower 

 Greensand, and says : — " The Shanklin (or Lower Green) Sand, 

 as I understand it, is the series of beds between the Weald Clay 

 and the Gault. But these sands at Potton are between the 

 Gault and the Oxford Clay ; and, so far as I remember, the 

 only fossil previously recorded from the beds in this district is 

 Ammonites biplex, mentioned in my paper on the Cretaceous 

 beds at Ely, — neither of which facts offers any presumptive 

 evidence of the deposit being Shanklin Sands." Here is his 

 statement in the paper he refers to : — " The lower part of the 

 Shanklin Sands is a conglomerate of small rounded pebbles, 

 which in the best place in the section is hardly moi'e than four 

 feet thick ; and above this are some brown sands alternating 

 irregularly with thin courses of clay with phosphatic nodules ; 



* Geological Magazine, vol. iii. p. 153. 



t This circumstance explains Mr. Brodie's apparent^ erroneous asser- 

 tion that " every organism in this phosphatic bed is evidently extraneous," 

 which was perfectly true with regard to the fossils obtainable when he wrote. 



