Vol. x1. 130 
difference in the grain of the shell, which does not, however, 
appear to be constant, except with those of cornix from 
Ireland, while I find the grain of the shell of eggs laid by a 
Blackbird mated with a Song-Thrush (of which I have one 
well-authenticated clutch, ‘Ibis,’ 1919, p. 160) to be inter- 
mediate, and have a much thinner glutinous layer than is 
normally present in the type-eges of the two species. 
The eggs of the coraz group present no external 
characteristics by which they can be safely separated. Size 
of individual specimens, or even in clutches, vary consider- 
ably, as will be seen by a clutch of four of frugilequs 
exhibited, in which there is considerable divergence in size. 
Nevertheless, I consider average weights in conjunction with 
measurements to be an almost infallible test for identi- 
fication. Weight alone in most cases would suffice, only in 
one or two isolated cases have I found them overlap. 
In weighing 50 British eggs of each (coraa, corone, cornia, 
and frugilegus), I find Rey’s average weights for frugilequs 
and corone less, and for corax considerably more, which is 
interesting if these weights are for continental eggs, which 
is probably the case. He does not appear to have weighed 
cornia egos. My weights are for Irish eggs only, which, 
as will be seen from the average given below, are considerably 
lighter than those of corone :— 
Weights (Bunyard’s). 
corax. corone. corm. Srugilegus. 
4 egas 8715 mg. 6-077 4292 4563 
5 6853, 5897 5350 3746 
s ig eos ae 4770 5058 3°908 
fp 7240 ,, 4:687 4-542 4:237 
0 B 202) 4°858 AAD) 4:285 
3 8018 ,, 5570 4'784 4:080 
- 6665 ,, 5°788 4-814 4788 
a 7423, 5066 4°365 4452 
” (ASNT 5 5'828 4385 4673 
average 36 1389 ,, 1:348 1-160 1:076 
The above weights are for four eggs, each from clutches 
of five and six, to show where there is slight overlapping. 
