A HISTORY OF NORFOLK 2^ inches in length, a size never attained in the river, nor, I believe, in the Wash itself. ' The position of the pits is about three-quarters of a mile from the Roman banks on the land side, and a mile and a half from the river Nene, up which the same species comes with the tide. ' There are many pits in this district in which the water rising from the silt is brackish, but I have never met with another case in which marine organisms were found living, though nearly every pit within an area of i,ooo square miles was examined. In some places a communica- tion is kept up with the sea by beds of quick-silt, and wells become distinctly brackish during high spring-tides. In the present instance such does not seem to be the case, and one is driven to the conclusion that the prawns must have been introduced accidentally, or that the ova were embedded in the silt itself. ' It is highly improbable that the prawns were introduced wilfully for the mystification of naturalists, for the latter are rarer than prawns about here, and the time of the appearance of the prawns just after the spring was tapped, and the fact of them all being very small at first are in favour of a natural mode of introduction. Neither is it probable that the ova were introduced by sea-birds in one of their very rare visits to this pit, for the ova are carried by the females until they hatch, and could not become attached to the bird, neither could they have survived the process of digestion as some seeds do. Besides, considering the great number of open pits hereabouts which have been unused for years, and so afford much better protection for sea-birds, the introduction of prawns ought to have been more general on such a supposition. True, most of the pits contain fresh, or only slightly brackish water, but prawns seem to live almost as well in fresh as in salt water, and I have frequently noticed them miles above locks on tidal streams, where the water is not even approximately brackish. The prawns in question were kept for weeks in fresh water, and they were then killed by accident. Neverthe- less, in no other pit have they been found, though they would hardly escape notice, since these spots afford valuable fishing resorts. ' The balance of evidence is decidedly in favour of the burial of the ova in the silt, which is so quick as to be dangerous to stand upon, and would afford plenty of water for their preservation. The only difficulty attaching to this supposition is the length of time during which the ova must have lain dormant. The Roman banks are about 1,700 years old, and at least 3,000 years must have elapsed since the area of the pits at the depth in question was covered with sea water. Yet I see no other explanation, and am strongly inclined to believe such to have been the case.' On this passage several comments may be made. The author seems to speak of prawns as if they all had the same habits and were all of one species. That he is really speaking of Palamonetes varians has to be inferred from the statement that specimens lived for weeks in fresh water. On the other hand, a size of 2| inches, though often 190
