414 Rev. Dr. Irving — Old River-Valley near Peterborough. 



a suggestive fact that their dead shells may be found in large numbers 

 in crannies in the rocks. The fossil specimens from some localities, 

 but not from others, are larger than the living forms. Two other 

 living species, P. bermudensts and F. circumfirmatus, are more widely 

 distributed and are fairly common. 



A most interesting account of tlie fossil land shells, by Professor 

 Addison Gulick, is to be found in the Proceedings of the Academy 

 of Natural Science of Philadelphia for July, 1904. There is still 

 work to be done in the study of the varieties of fossil species from 

 different localities and in tracing the connexion between the fossil 

 and living forms. 



II. 



The analysis of the phosphorite rock, described at the end of the 

 article, suggests an interesting problem. Flat bottoms among the 

 reefs, at any rate in the more sheltered channels and sounds, consist 

 of chalky mud, reduced to its present state in the intestines of the 

 big holothurians, known locally as 'sea cucumbers'. It is possible 

 that a similar oingin for the rocks analysed would account for their 

 coprolitic nature. The qiiestion of how such an ancient sea bottom 

 came into its present position would still have to be tackled, but the 

 theory now suggested seems at least more tenable than that of deep 

 sea mud referred to as impossible on p. 440. 



Although there is every proof that the islands have been sinking 

 during past ages, there have been some slight upheavals, if only 

 local, as evidenced by the so-called Devonshire formations containing 

 marine shells {vide p. 393). 



VI. — Note on a Biteied (East Mercian) ^ River Channel near 

 Peterborough. 



By A. Irving, D.Sc, B.A. 



IN the Peterhorough Adfertiser for December 16, 1911, there 

 appeared an illustrated article on a "recent discovery" of 

 a silted-up pre-glacial river-valley, 250 yards wide, at Fletton, near 

 Peterborough. Eliminating from that article a good deal of scientific 

 romance, there remains a certain residuum of geological facts, so far 

 as the determination of them by the writer of this note has been 

 carried out, through the courtesy of Mr. A. Adams, the Manager of 

 the London Brick Company's works. 



The banks of the ancient river appear to be well defined on the 

 north and south sides of the buried channel. Against these there 

 lies a deposit of slimy river-silt derived from the material of the 

 Oxford Clay, through which the river (comparable with the Trent at 

 Newark) had carved out its course. This black silt contains fossils 

 of the Oxford Clay itself, along with shells of Cardium edtde -, and 



^ Eead at the British Association, Dundee Meeting (1912), Section C. 



- Determined by Mr. K. B. Newton at the British Museum (Nat. Hist.). 

 Mr. G. Wyman Abbott, of Peterborough, is preparing a paper on the shell- 

 contents of these beds in co-operation with a well-known specialist on 

 recent shells. 



