I propose this genus for the reception of a remarkable Flower-pecker which is found only in Ceylon and which has hitherto been placed either in Prionochilus or in Pachyglossa. It differs from both these genera in possessing only nine primaries. From Dicaeum it may be recognized by its very large, coarse bill, and from Piprisoma by its rounded tail and the numerous hairs which cover the nostrils.
In Acmonorhynchus the sexes differ and the young bird resembles the female. Its habits are those of the family, but nothing is known about its nidification.