Chthonerpeton indistinctum (Reinhardt & Lütken 1862)

It is a typhlonectid with a body length between 99 and 530 mm and 70 to 80 incomplete primary body annuli. Secondary annulli are absent, and the skin is smooth. The dorsum is bright black, the venter is black-gray, and both are covered with minute white spots. In addition, The tentacle and the eye are surrounded by a whitish area which can or cannot be continuous. The disc area surrounding the vent is cream-white. The nostrils are dorsolateral and closer to the snout than to the eyes, and the tentacle extrudes midway between the eye and the snout. The skull is similar to that ot other typhlonectids, but with an open tentacular groove that crosses the maxillopalatine. The quadrate and pterygoid are completely fused.

C. indistinctum is found in temperate South America, in the Rio de la Plata basin and in drainages along the adjacent coasts.