on the Topography of a Bird. 163


Careful attention must be paid to the form of the nostrils.

In some birds, as in the New World Vultures, these are pierced,

and are then said to be perforate ; when the nostrils of the two

sides are separated by a partition they are said to be imperforate.

Often this aperture is guarded by a scale or operculum. I11

some birds, as in Gannets and Cormorants the nostrils are want¬

ing. The length and shape of the beak will, of course, also be

noted.


The legs and toes are generally encased in a horny sheath,

the podotheca. When this sheath is divided into a number of

small pieces it is said to be schizothecal. I11 most cases these

pieces take the form of moderately large shields, when the

sheath is said to be scutellate; when the shields are small and

octagonal in shape, reticulate. Sometimes the back of the tarso-

metatarsus or planta is invested in a pair of plates meeting one

another in the middle line ; this arrangement is known as lamini-

plantar. This character is a conspicuous feature in the sub¬

division of the Passeres. A still further fusion of plates, resulting

in the formation of a continuous sheath along the front of the

leg, or acrotarsuwi, results in what is called a liolothecalpodotheca,

e. g. Robin. Generally it will be found this sheath is composed

of scales of various kinds ; thus the lower portion of the acro-

tarsium may be scutellate, the upper portion reticulate ; similarly

th e planta may be clothed partly in scutellae, partly in reticulated

plates.


Sometimes these scales give place to a thin skin marked

with fine lines as in the Duck ; the sheath is then said to be

cancellated.


In certain birds of prey, Owls and Grouse, the scaly cover¬

ing is replaced by feathers, which may even clothe the “ soles ”

of the feet.


The under surface of the toes in birds of prey have large

fleshy tubercles at the joints ; these are known as tylari.


The form of the claws should be carefully noted. Often

the claw of the middle toe has a comb-like edge, when it is said

to be pectinated or serrated.


The general form of the foot varies greatly. Normally



