2 Mr. W. C. Williamson on the Recent 



Dr. Mantell supplied me with specimens from a similar accu- 

 mulation at Marcli in Cambridgeshire, equally rich in the same 

 elegant organisms. On comparing these with such published 

 drawings and descriptions of Lagence as were available to me, it 

 was very evident that both the one and the other were exceed- 

 ingly incomplete, the drawings being for the most part unre- 

 cognizable caricatures, and the descriptions not comprehending 

 half the forms that had come under my notice. Contemplating 

 the production of a brief monograph on the subject, I wrote to 

 J. Gwyn Jeffreys, Esq. of Swansea, soliciting his valuable aid, 

 knowing that he possessed an excellent series of these interesting 

 objects from various British localities. In reply he informed me, 

 that in 1828 he had laid before the Linnsean Society a memoir on 

 the same genus, which memoir the Council of the Society ordered 

 to be published in their ' Transactions.' Mr. Jeffreys however, 

 not being satisfied on some points connected with the natural hi- 

 story of these animals, declined publishing the memoir until he 

 had carried out further investigations, and consequently it was 

 not printed. 



This memoir, embodying his views of the genus up to that 

 comparatively early period, he has kindly placed in my hands, 

 and also, with that generous liberality which characterizes the 

 true philosopher, he has forwarded to me his entire collection of 

 Lagence to be used as I thought proper. 



Under these circumstances I resolved upon a revision of the 

 genus, giving figures of all the known British species, believing 

 that the monograph would be neither useless nor uninteresting 

 to the students of these microscopic organisms. The Boston and 

 March deposits have enabled me, from their productiveness, to 

 compare an immense number of specimens, and the two collec- 

 tions of Mr. Jeffreys and Mr. Bean of Scarborough have afforded 



common of our British species. The specimen from March, which Dr. Man- 

 tell has placed in my hands, confirms my view as to the extent of this marine 

 deposit. I have little doubt that it extends over the greater part of the Fen 

 district, and probably it will be found to be continuous with the existing 

 beaches of the coasts of Lincolnshire and Norfolk. The most curious fea- 

 ture of the deposit, as it exists at Boston and March, is the young state of 

 nearly all the organisms found in it. The specimens oi Rotalina Beccarii, 

 Polystomella criapa and Qninqueloculina seminulum rarely exceed the -^th 

 of an inch in diameter, which, with their highly translucent aspect, shows 

 them to be in a very young state. The same remark applies, though in a 

 less degree, to the Lagence : does not this most strikingly illustrate the sift- 

 ing power of aqueous currents, and explain the way in which such differ- 

 ences have been produced in rocks, which, like the chalk, have been entirely 

 formed by an accumulation of Foraminifera and other small organisms, 

 which in some localities are exceedingly minute, forming very fine-grained 

 strata, whilst in others they are comparatively large, forming deposits of 

 coarse texture? 



