The identity of Azara's No. 239 "Cola aguda cola sanguina" has never been convincingly elucidated and the only previous proposed identity as Plain-crowned Spinetail Synallaxis gujanensis is demonstrably incorrect. Azara provides a brief and imperfect, but diagnostic description of a bird which is clearly in the genus Synallaxis, of which eight species occur in Paraguay. The description of the crown being concolorous with the upperparts, the wing and tail pattern, and the measurements provided are sufficient to eliminate all species as candidates except the Grey-bellied Spinetail Synallaxis cinerascens, a common bird of Paraguayan Atlantic forests in the Oriental region of the country. To my knowledge, no scientific names have been proposed on the basis of this description.