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XXVIII. 
REPORT ON LAND AND FRESH-WATER MOLLUSCA OBSERVED 
IN HERTFORDSHIRE IN 1910. 
By Charles Oldham, E.Z.S., M.B.O.U. 
Read at Watford , 27th March, 1911. 
On the occasion of the field meeting at the Watford Gras Works 
on April 2nd, I obtained a quantity of shell-marl from the 
alluvial deposit which at one time formed the river-bed of the 
Colne. Mr. E. T. Newton, F.R.S., considers, from an examination 
of the remains of wild and domesticated mammals which this 
deposit contains, that it is not older than the Roman period. It 
is rich in Mollusca; the material that I washed and sifted 
yielded twenty-one species. Of these, twelve—marked with 
an asterisk in the subjoined list of all the species hitherto 
discovered—are not mentioned in Mr. J. Hopkinson’s list, which 
appeared in the Society’s ‘ Transactions ’ for 1906 (Yol. XIII, 
p. 80) ; but on the other hand I failed to find thirteen species— 
marked with an obelisk—-which he mentions. 
*Vitrea nitidula (Drap.). 
*Euconulus fulvus (Mull.). 
fPyramidula rotundata (Miill.). 
fHelicella caperata (Mont.). 
*Hygromia hispida (Linn.). 
# Vallonia pulchella (Miill.). 
Helicigona arbustorum (Linn.). 
Helix nemoralis Linn, 
f H. hortensis Miill. 
Cochlicopa lubrica (Miill.). 
Jaminia muscorum (Linn.). 
Succinea putris (Linn.). 
# Carychium minimum Miill. 
Limnsea pereger (Miill.). 
L. palustris (Miill.). 
# L. truncatula (Midi.). 
# L/. stagnalis (Linn.), 
t Planorbis albus Miill. 
fP. glaber Jeffr. 
fP. carinatus Miill. 
*P. umbilicatus Miill. 
P. vortex (Linn.). 
fP. spirorbis (Linn.). 
fP. contortus (Linn.). 
fSegmentina nitida (Miill.) = Planorbis lineatus Walker, 
f Physa fontinalis (Linn.). 
Bithynia tentaculata (Linn.). 
*Valvata piscinalis (Miill.). 
*V. crist at a Miill. 
VOL. xiv. —PART IV. 
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