THE 
4 
Essex Naturalist: 
BEING THE 
Journal of tbe iBsser jfielO Club. 
EDITED BY 
PERCY THOMPSON, F.L.S., Honorary Secretary. 
x 
VOLUME XX. 
APRIL 1921 to OCTOBER 1923. 
“ Men that undertake only one district are much more likely to advance 
Natural Knowledge than those that grasp at more than they can possibly be 
acquainted with. Every kingdom., every province, should have its own 
Monographer .”-— -Gilbert White, of Selborne. 
“ Things seen are mightier than things heard .”— Tennyson. 
/ 
[The authors alone are responsible for the statements and opinions contained in their 
respective papers .] 
J&frdfforb, (&BBex : 
THE ESSEX FIELD CLUB, AT THE ESSEX MUSEUM 
OF NATURAL HISTORY. 
1924. 
