520 
MR MACGILLIVRAY ON THE 
cies of a genus, it has been thought sufficient, where the 
colour was laid out in mass, a principal tint pervading the 
greater part of the plumage, to epitomise the whole by a 
general expression, adding to this one or more of the 
colours by which the subordinate parts were marked ; or, 
where the colours were distributed in patches, to select the 
most striking, or seemingly characteristic. For example : 
Trocliilus moscJiitus ; T. viridescens, vertice purpureo 
aurato, gutture auroreo-rutilo. Blum. 
Parus major ; P. capite nigro, temporibus albis, nucha 
lutea. Blum. 
And various other modifications of the same principle 
have been used, according to the particular circumstances 
of the case. 
The feathers, however, are not the only parts whose 
colours have been thought of sufficient importance to fur- 
nish specific characters: the bill, the eyes, the legs, the 
claws, the wattles, and other appendages, have also afforded 
marks of this kind. For example : 
Falco communis; F. rostro coerulescente, cera iridibus 
pedibusque luteis. Lath. 
Vultur pofidicerimius ; V. capite colloque, incarnatis, 
lateribus colli caruncula, rubra. Lath. 
The colour of the iris, in particular, has been assumed as 
a character to which much importance has been attributed, 
and which Beisson, Montagu, Temminck, and others, 
seem to have regarded as an infallible criterion. Thus, for 
example, the last-mentioned ornithologist, in giving what 
he considers as the distinctive characters of the raven and 
carrion-crow, describes the iris of the first as being " a 
