The oval, rugose carapace has unserrated marginals, and a low medial keel on vertebrals 3-4. No size data were included with the original description, but a female paratype in the Smithsonian Institution (USNM 329467, originally MZUSP 3226) has a 14.4 cm carapace; plastron length is up to 14.7 cm (Paulo Vanzolini, pers. comm.). Vertebral 1 is broad and urn-shaped (constricted anteriorly); vertebrals 2-5 are broader than long, with the 5th flared posteriorly. Ground color is green to olive-brown with a pattern of large, black-bordered, reddish orange-centered, ocelli on each pleural scute. Each vertebral bears two narrow orangish, longitudinal stripes, and each upper marginal has a reddish orange bar. The hingeless plastron is yellow with an elaborate pattern of broad, olive-gray, dark-bordered lines, but no medial, longitudinal dark mark. Each bridge bears dark longitudinal bars, and a dark-bordered ocellus is present at the posterior edge of each lower marginal. The anal scute is slightly notched; the plastral formula is abd > an > gul > pect > fem > hum. The head is narrow with a slightly upturned, protruding snout and a medially notched upper jaw. The head is black on top, and yellow prefrontal arrow may be present. The broad yellow postorbital stripe contacts the orbit via a narrow isthmus. The chin and throat bear an inverted Y-shaped, yellow mark.
Males have long, thick tails with the vent beyond the posterior carapace rim.
This turtle is known only from Santa Amaro, Maranhão, Brazil.
Trachemys adiutrix lives in sand-bottomed permanent ponds in the dune-fields of Maranhão, Brazil. It wanders on land during the rainy season, but buries in the sand and aestivates during the dry season.
Females usually lay clutches of 11-12 hard-shelled eggs, but one gravid female contained 24 eggs indicating two clutches per season.
T. adiutrix is very similar to and may prove to be a subspecies of T. dorbignyi.
IUCN Red List Status (1996)