The generic definition of Sonatsa Chamberlin is revised to include Maldaninae polychaetes with a long and convex cephalic keel, nuchal organs that diverge posteriorly, 2 preanal asetous glandular pads, an enlarged glandular pad on setiger 5, and a large decrease in the number of uncini from setiger 5 to setiger 6. Neuropodial uncini occur in a single row, which may be uneven due to crowding. Uncini do not occur in 2 or 3 rows as originally described. Sonatsa meridionalis Chamberlin, 1919, is emended and its range extended based on examination of the holotype and additional material. Maldane carinata Moore, 1923, is resurrected from synonymy, redescribed, and reassigned to Sonatsa.