oji the Beak 0/ a Nestling. 271


The size and shape of the beak of this specimen at once

caught my attention, and further examination revealed other

characters of interest, which, I think are of sufficient importance

to be worth bringing to the notice of the readers of the

Avicultural Magazine.


In so far as size and shape are concerned, I may remark

that in this nestling the beak was relatively very much shorter

than in the adult, and more strongly arched along the culmen.

But these points are of no great importance. The facts to which

I desire to draw attention here, concern certain peculiarities

observable along the tomia of both upper and lower jaws.


In the first place, the cutting-edge of the lower jaw in this

nestling is exposed along its whole length ; and furthermore,

rises upwards 011 either side of the upper jaw, so as to conceal

the hinder portion of the cutting edges thereof. In other words,

the lower jaw, in so far as its hinder half is concerned, at any

rate, forms a kind of trough into which the upper jaw is received.

In the adult, the cutting edges of the upper jaw embrace, the

sides of the lower extending downwards so that the tomium of

the mandible is completely concealed. This of course is the

normal relation which obtains in the closed beak among birds.


These jaws are further peculiar in that their cutting-edges

have not yet cornified, but remain soft and membranous 011 either

side, up to within a short distance of the tip of the beak.


There remains yet one other point to mention, and this not

the least remarkable. Just behind the curiously striated tip of

the upper jaw, is a well-defined notch, formed apparently, to

receive the cutting edge of the lower jaw, as they approach one

another at the symphysis.


The " curiously striated tip" to which I have just referred

demands further study, and later I hope to lay before the readers

of this Magazine the results of my research.


The beaks of nestling birds always deserve careful study :

for while in some they present undoubted ancestral characters,

in others they show 110 less evidence of having undergone

peculiar modifications to serve the ends of later requirements.

Whether the features to which I have just drawn attention are to

be regarded as belonging to this later " ueogenetic " phase,



