The Bulbuls of this genus are very close indeed to Molpastes but the feathers forming the crest spring from the centre of the crown, the feathers of the hind crown being short and of the usual character. In our Indian forms the crest is very long but in the Burmese forms less conspicuously so and in O. flaviventris johnstoni from East Siam it is quite short.
From the next genus, Pinarocichla, it is easily distinguished by its soft plumage on the lower back and rump.
Key to Species and Subspecies.
A. Upper plumage brown, no green or yellow in plumage.
a. Upper plumage a rich ruddy-brown .... O. emeria emeria, p. 394.
b. Upper plumage dull brown.
a1 Tail-feathers with no white tips .... O. a. fuscicaudata, p. 396.
b1. Tail-feathers with white tips O. e. peguensis, p. 396.
B. Plumage nearly all green and yellow except head. [p. 397.
c. Larger, wing average about 85 mm O. flaviventris flaviventris,
d. Smaller, wing average about 81 mm O. fl. minor, p. 398.