KENNARD & WOODWARD: ON NERITINA GRATELOUPIANA. SA 
in countless myriads, the coloration being preserved in a very striking 
manner. A few examples are pure white, without any trace of 
markings, whilst in others the ground colour is almost obscured by 
the markings, and every gradation between these is met with. The 
average size is 9mm. in height by 10 mm. in breadth, but exceptional 
specimens were 10mm. by 13mm. About 80 per cent. of the 
examples possess crenulations on the edge of the columella lip, but 
the size of the crenulations is by no means constant. It is remarkable 
that not a single example of the operculum has been found, though 
a careful search was made. 
We have here an extremely interesting example of the imperfection 
of the paleontological record. Unknown in any deposit on the 
continent of later age than the Upper Miocene, it suddenly appears 
in the Pleistocene of the Thames Valley in countless profusion, and 
it is unknown in any later deposits, whilst the living English species, 
N. fluviatilis, though known from the Miocene of Germany, is quite 
unknown in these Islands in any deposit older than the Holocene. 
It is only within the last few years that these recent deposits and 
their contained fauna have received any adequate attention, and we 
venture to think that the problems they present are as interesting as 
any in the domains of malacological science. 
VOL. V.—-JUNE, 1903. 22 
