386 A FIRST LIST OF THE BIRDS 
Tenasserim with 22 others from the Assamboo Hills in the 
extreme south of India, the Dhoon, Sikhim, and Cachar, I 
cannot see my way to making more than one species out of the 
birds that occur within the limits of our Indian Empire. 
There is no doubt that the Sikhim birds are, some of them at 
any rate, larger than those from Tenasserim and even Southern 
India, but in a large series, such as I have now before me, every 
gradation of size is to be met with; and so far as plumage and 
colouration of bill and casque are concerned, there is absolutely 
not the smallest constant difference between specimens obtained 
in different parts of the country. 
As regards the shape of the casque there is undoubtedly the 
most conspicuous difference between different specimens. Hold- 
ing the point of the bill towards one, and looking at the anterior 
margin of the casque, this margin in some specimens assumes 
the shape of a semi-circular curve, at times of a curve even 
deeper than a semi-circle, while again in other specimens it is a 
curve so flat as scarcely to deserve the name of a curve. In 
one specimen, for instance, from Darjeeling, the two anterior 
points of the casque are 3°5 inches apart; but the lowest point 
of the casque between these two points is only 0°35 below them. 
In another specimen, and this is from Kollidoo, the points of 
the casque are only 2°1 apart, and the lowest point of the casque 
between these points is 1:25 below them. 
I believe that the former represents what Mr. Gray consi- 
dered to be homrai of Hodgson, the latter what he considered to 
be bicornis. It was looking to these differences at a time when 
I had no opportunity of comparing a large series that I, in the 
first list of the birds of the Tenasserim Provinces (ante Vol. 
II, p. 470), separated the specimens obtained by us in Tenasser- 
im into these two species; but I am convinced, now, that this 
distinction will not hold, as specimens from all localities equal- 
ly present these differences, and this in what are obviously 
old adults. 
Even from the same localities the size of the bill and 
casque varies greatly amongst apparently perfect adults ; 
but unquestionably, as a whole, the Sikhim birds have them 
larger than any obtained elsewhere. 
In one Sikhim bird, the bill and casque together measured 
from the posterior margin of the casque along the middle of the 
casque and culmen to. point, measures 17: 5 inches, and the 
ereatest height of bill taking the two mandibles and the casque 
together i is 5 inches ; ; another Sikhim bird is 17°75 and 5 inches, 
and there are several Sikhim s specimens over 17 and 4°75 inches. 
On the other hand, the largest South Tenasserim specimen mea- 
sured in this same way is only 16 and 4:5. The rest average 
