From Blanchard (1972)
(1):
Oncocnemis cottami is very close to
O. atricollaris Harvey. The transverse lines of
atricollaris are generally well marked, sometime only partly traceable, rarely completely obsolete; the part of the reniform which falls below the upper black fascia generally shows as a pure white small pupil; the white median band of the collar appears narrower because its top half is much soiled with brown scalcs. If all three of these characters appear doubtful, one has to rely on the genitalia to remove all doubt.