[English text with extensive resume in Portuguese. Introduction as follows:]
In Dr. Harald Sioli's amazonian collection, the Oligochaetes and Nemertines of which were already studied by Eveline du Bois-Reymond Marcus (1947 and this Bulletin, p. 93), there were 20 specimens and fragments of Polychaetes. I am indebted to Mrs. Marcus and to her husband for having intrusted me with the interesting material and assisted me in the elaboration of the present paper.
The samples were gathered at the following localities:
River Tapajóz, near Santarém (Pará), in 28 m. depth (22. II. 1941).
River Tapajóz, about 40 km. upstream, in 10 m. depth. Belterra, Ford's rubber plantation (20. IV 1946).
River Tapajóz, lake Pindobal (15 and 18 m.), Belterra (5 and 11. VI. 1946).
The material is uniform and represents a new species of the genus
Lycastis Savigny 1822 (Audouin & Milne Edwards 1833 emend.),
Lycastis siolii, named after the meritorious collector.
