1871.3 199 
considerable tracts of green-sand on the side of the county bordering 
the fen valley, but this formation in other parts of England is found no 
more favourable to coast sand-hill insects than any other. 
As nobody will, F suppose, venture to suggest that there has been 
a special creation for this little spot, the only reasonable conclusion to 
be arrived at, in my opinion, is, that these species have occupied this 
suitable ground from the time of the close of the Post-Glacial period, 
at least, and previous to the upheaval of the present fen valley, and 
that they have remained unchanged in form, and even in colour, through 
the many conditions of life comprised in so long a period, and in par- 
ticular that of the change from the saline influences of a neighbouring 
sea, to those of a warm inland district. 
One slight change of habit is apparent, due doubtless to the 
higher temperature. All these species were out on June 4th, desertella 
in swarms, and a week later Jotella was common, and albicolon getting 
worn, while at this latter time abicolon and desertella were just begin- 
ning to come out at Yarmouth, and the other species were not to be | 
found till a fortnight later, July being their time of appearance on the 
coast. 
Since this subject has occupied my attention, I have received some 
valuable confirmatory evidence. Mr. de Grey informs me that he has 
taken Agrotis cinerea, Gelechia vilella, and G. pictella, at Brandon, and 
G. marmorea on a portion of the Merton estate to which this drift 
sand extends. The Rev. H. S. Marriott of Wickham Market, and 
Rey. H. Williams of Croxton, report, not only Mamestra albicolon and 
Anerastia lotetla, but also Hubolia lineolata and Agrotis valligera occur- 
ring commonly on the sands round Thetford, the former on grassy heaths 
and the latter flying over lucerne fields. And, in addition to all this, 
I hear from Henry Stevenson, Esq., F.L.S., author of “The Birds of 
Norfolk,” that a colony of the Ring Dotterel (Charadrias hiaticula), a 
bird which breeds exclusively on coast sands, has bred upon Thetford 
Warren from the time of the earliest records, and was then immensely 
more numerous than within the last fifty years; and that it is his 
opinion, and that of Professor Newton, from their knowledge of the 
habits of some birds, and the persistency with which they return to 
breed in the place where they were reared, that these Ring Dotterels 
have occupied the same spot in uninterrupted succession from the time 
when the Thetford and Brandon sands lay on the shore of the Post- 
Glacial sea until the present day. 
There is an interesting point which I have not touched upon. | 
