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XI. 



OSTRACODA AND MOLLUSCA FROM THE ALLUVIAL DEPOSITS 

 AT THE WATFORD GAS WORKS. 



By John Hopkinson, F.L.S., F.G.S., P.E.M.S., etc. 



Rind at Watford, 2nd April, 1906. 



The Alluvial deposits of Holocene age, exposed at the Watford 

 Gas Works in excavating for a new gasometer, were examined at 

 a field meeting of the Society on the 3rd of May, 1902, and 

 a paper describing them was read before the Society by 

 Dr. T. E. Lones, and puljlished in our ' Transactions,' Vol. XII, 

 p. 18. An account of the field meeting appeared in the previous 

 volume (XI, p. xli). In this account I gave a list of eighteen 

 species of land and fresh-water Mollusca then collected in the 

 grey marl which formed the old river-bed of the Colne when 

 flowing at a considerably higher level than it does at the present 

 time. Suspecting the occurrence of Ostracoda in this marl, 

 I sent, a few days later, a small box-full to Mr. Frederick 

 Chapman, A.L.S., who has made a special study of this subject, 

 and has contributed a paper to our Society on " Ostracoda from 

 the Chara-Marl of Hitchin." Unknown to me, Mr. Chapman 

 had then left this country for Australia, and a few months ago 

 I received from him the following letter, written from the 

 National Museum, Melbourne, 6tli September, 1905 : — 



" Some years ago (17th May, 1902) you very kindly sent, to 

 my London address, which I had then left for Melbourne, a box 

 of loam from the old bed of the Eiver Colne at Watford, in the 

 hope that it might yield some forms of Ostracoda. When the 

 material reached me in Melbourne I believe I wrote to you 

 concerning it, and promised to look at it later on. My friend 

 Mr. A. D. Hardy, of the Lands Department, Melbourne, told me 

 the other day that he had heard from you, and reminded me of 

 my promise to look at the Ostracod material. I am sorry that 

 you should have had to wait so long for my response, and I send 

 hei'ewith the results of my exaniiuation of the sample. . . . 



" Ostracoda. — Well-preserved but exceedingly rare ; one 

 specimen only of each of the species mentioned : Gandona 

 Candida, 0. F. Miill. ; G. pubescens, Koch ; Ilyocystis Bradii, 

 Gr. 0. Sars ; Limnicythere inopinata, Baird. 



" Mollusca. — Helix rotundata, Miill. ; Succinea putris, Linn. ; 

 Planorbis albus, Midi. ; P. gJaber, Jeffr. ; P. lineatus, Walker ; 

 Bythinia tentaculata, Linn, (opercula only) ; SpJieerium corneinn, 

 Linn., var. pisidioides, Gray." 



Mr. Chapman's communication not only adds to our sub-fossil 

 fauna four species of Ostracoda, but also adds four species of 

 Mollusca to those before determined, these species being 

 Planorbis albus, glaber, and lineatus, and Sphxrium corneutn. 



