302 
MR. W. G. CLARKE ON VERTEBRATE ANIMALS 
classed as semi-domesticated. These species have been divided into 
53 common, 43 rather rare, 29 rare, and 59 accidental, in which 
division also, those birds which are now practically extinct have 
been placed. The large proportion of 102 species are known to 
breed in the district. The most curious feature in the fauna of 
Thetford district is the occurrence on our inland heaths and warrens, 
of plants, insects, and birds, whose habitat is generally confined to 
the sea coast. Many eminent authorities, amongst them Professor 
Newton and the late Dr. Hind of Honington, Suffolk, think that 
an arm of the Wash may have reached Thetford from the west by 
the present Little Ouse valley, in the post-glacial epoch, and that 
these heaths are formed of the coast sands — a very probable theory. 
It is thought unlikely that the sea could have come in from the 
eastward. According to this theory, it is hereditary instinct which 
has brought the Pinged Plovers inland each year with the return 
of spring, a habit transmitted to generation after generation from 
the post-glacial period. The first President of the Norfolk and 
Norwich Naturalists’ Society, in his presidential address in March, 
1870, remarked: “I would further hazard an opinion that with 
the death of the last of these warren-haunting Plovers, would cease 
altogether the appearance of that species (Ringed Plover) on the 
‘breck’ sands of Norfolk and Suffolk.” Another particularly 
noteworthy fact is the inland breeding of seven species of Wild 
Duck, on the meres of Wretham Heath and Park ; and also the 
nesting of the Redshank on one particular meadow in the district 
yearly. 
Twenty- four species of Fish have been identified, of which 18 
are classed as common, 3 as rather rare, and 2 as rare ; whilst the 
Sturgeon is practically extinct. That fish are plentiful in the meres 
as well as rivers is proved by the fact that an angler in Fowlmere 
caught over one hundredweight of coarse fish in one day in 1897. 
During the present century, Thetford district lias rarely been 
without some resident naturalists of repute. Perhaps the most 
famous of these, as a resident, was John Drew Salmon, F.L.S., a 
well-known oologist and botanist, who resided in Norfolk, at Stoke 
ferry and lhetford, from 1825 to 1837, living at Thetford the 
last four years; he died in London in 1859. Part of his oological 
collection he left to the Linnean Society, and his herbarium and 
diary to Norwich Museum, of which he was an honorary member. 
He contributed much to ‘Loudon’s Magazine of Natural History.’ 
