[None. Introduction begins:]
Dr. Mortensen kindly did me the honour of asking me to report upon his Panama collection of Polychaeta, and the following paper deals with all the families represented in it except the Polynoidae and Acoetidae. The examples of the two latter families have been described in a separate publication jointly with those collected bv Dr. C. Crossland from the same region. The fauna of the Panama coasts is tropical, and the forms here studied confirm Prof. P. Fauvel ’s contention that among the Polychaeta the tropical fauna includes many species common to the Atlantic, the Pacific and the Indian Oceans.