This species is generally a rather large tree, to ca. 20 m tall, with elliptic glabrescent leaves, sericeous calyptrate stipules, the flowers grouped in short cymes along well developed secondary and tertiary axes (producing a weakly spiciform appearance), small green corollas, and somewhat small ellipsoid capsules. The leaves have a characteristic subparallel arrangement of the tertiary veins and generally also a distinctive brown or yellowish brown drying color (which is not unique to this species).

Bathysa perijaensis is similar to Bathysa bathysoides; they were originally separated by details of pubescence, in particular composed of appressed trichomes in Bathysa bathysoides vs. spreading trichomes in Bathysa perijaensis, with each of them known from two specimens. These species do appear to be distributed in notably allopatric ranges. Bathysa bathysoides is much more widely documented now in the Amazon basin, appears to differ in its larger capsules; however Bathysa perijaensis is still poorly known.