part 3] MOLLUSCA FBOM THE CAMBRIDGE GBATELS. 23] 



the number to forty-four, 1 while in 1872 Mr. Alfred Bell added 

 eleven more species,- and in 1878 A. J. Jukes-Browne published 

 a list of fifty-eight species. 8 In 1881 appeared the Geological 

 Survey Memoir, but the list there published is open to severe 

 criticism, and added nothing to our knowledge. 1 Two years later 

 Prof. T. McKenny Hughes gave a list of the species in the 

 Woodwardian Museum. 5 In 1888 Mrs. Hughes published a full 

 description of these deposits, giving a detailed account of the 

 mollusca, while in the same year one of us (B. B. W.) critically 

 revised the previous records, and from an examination of the 

 extant examples extended the list to sixty-seven species, Clausilia 

 pumila C. Pfeitfer being figured as British for the first time. 7 



Since then the only additions have been those species of Pisidium 

 detected during the revision of that genus. 8 In 1916 the late 

 Prof. T. McKenny Hughes described in much detail the deposits 

 which he considered to be Postglacial. He discussed the con- 

 flicting evidence furnished by the contained fossils, and concluded 

 that these beds and their supposed equivalents, which he traced 

 over a large area, formed a well-marked stage in the Pleistocene, 

 for which he proposed the name Barnwellian. 9 In the same year, 

 however. Dr. J. E. Marr & Miss E. W. Gardner published an 

 important paper on the Barnwell-Station Pit, and from the palaeo- 

 botanical evidence concluded that this deposit was of the same age 

 as the Glacial beds of the Kiver Lea. 10 We had previously arrived 

 at the conclusion that more than one zone was represented at 

 Barnwell, from the fact that certain species of mollusca known 

 from Barnwell indicated a much later zone than the bulk of the 

 species, and it was now clear that at least two zones were repre- 

 sented in the Barnwell gravels. In these circumstances we have 

 deemed it advisable to register the shells from the various sections 

 separately, and with interesting results. 



Barnwell Abbey. 



The classic sections at Barnwell Abbey are now 'things of the 

 past,' and, though gravel is still being dug in the neighbourhood, no 

 mollusca are obtainable. In past years, however, when the shells 

 were abundant, the collecting of these fossils was quite fashionable 

 among the students at Cambridge, and numerous collections were 



1 Q. J.G.S vol. xxii. p. 477. 



- Proc. Geol. Assoc, vol. ii, p. 222. 



3 ' The Post-Tertiary Deposits of Cambridgeshire ' Sedgwick Prize K>-a\ 

 for 1876, p. 64. 



4 'The Geology of the Neighbourhood of Cambridge 9 Mem. Geol. Surv. 

 Sheet 51S.W., pp. 106 107. 



5 Geol. Mag. dec 2. vol. x (188:*) p. l.V>. 



6 Ibid. dec. 3, vol. v U888) pp. 193 207. 



7 Proc. Geol. Assoc, vol. x. pp. 355 60. 



8 B. B. Woodward. ' Catalogue of the British Speoies of Pisidium, &c.' 1913. 



9 'Gravels of East Anglia ' Cambridge, pp. 38 ~> s . 

 10 Geol. Mag. dec. 6. vol. iii (1916) pp. :::'.!' 13. 



