Diagnosis: body naked, slender, elongated and cylindrical, ending in a very tapering point; the caudal part of the body makes less than one third of the total length; no trace of paired or unpaired fins; eye atrophied, deep-set under skin, practically invisible from the outside; conical teeth on jaws and palate; gill opening minute, reduced to a median ovate pore, surrounded with longitudinal skin folds; 4 branchiostegal rays; 3 branchial arches without branchial lamellae; lateral line present; vertebral count: 140-144 abdominal and 39-45 caudal (Ref. 57291).

Colouration: uniformly dark (Ref. 57291).