ACOMUS 
CRESTLESS FIREBACK PHEASANTS 
Family PHASIANIDAE 
Subfamily PHASIANINAE 
Genus ACOMUS 
Tus small genus of pheasants is unquestionably rather closely related to the 
crested firebacks (Lophura) and more distantly to the silver pheasants (Gennaeus), 
but instead of lumping all three, and thereby relegating their differences to the obscurity 
of subgeneric rank, I consider that the groups are sufficiently distinct to warrant giving 
to them full generic value. 
The chief point of difference between comus: and Lophura is the extremely 
masculine pattern and colour of the plumage of the females in the former genus, together 
with the less important total absence of crest in both sexes and the very small size. 
The side of the head is bare and covered with fine papillae ; the wattles are very small, 
but the bill is of moderate size; the tarsus is extremely long, its length relative to that 
of the middle toe and claw being 3:2; the primary formula shows the 1st much shorter 
than the 2nd, which is about the length of the 1oth, the 6th being slightly the longest. 
The tail is composed of fourteen feathers, quite short and compressed laterally, like that 
of a domestic hen. The third pair is the longest, the outer being considerably ‘the 
shortest of the seven. Spurs are present in both sexes. The general colour is bluish- 
black, the males having white vermiculations or streaks, highly iridescent back and 
rump, and buff tail-feathers. 
The Crestless Firebacks number two well-known distinct species and a third 
extremely doubtful one. For reasons given elsewhere I shall not recognize this latter 
form in my treatment of the genus. They are confined to the southern part of the 
Malay Peninsula, Sumatra and Borneo. 
Malayan Crestless Fireback : : : : : Acomus erythrophthalmus (Raffles). 
Bornean Crestless Fireback : : : : Acomus pyronotus (Gray). 
KEY TO ACOMUS 
I, Plumage not uniform bluish-black (males) 
(a) Breast almost uniformly dark. : : : : ‘ : erythrophthalmus. 
() Breast with conspicuous white shaft streaks : s . — pyronotus. 
(il. Pappagecmieny sissy GueGa. Gun sane Leen { erythrophihalnus. 
pyronotus. 
(Pyronotus females average slightly larger, and show somewhat stronger bluish gloss, but variation is too 
great to render these characters of diagnostic value.) 
IOI 
