The black-bellied slender salamander is about 3.1 to 4.3 cm long. It has a worm-like body, a small head and small limbs, and a long cylindrical tail, often twice the length of its body. The black-bellied slender salamander can have a black, tan, reddish, brown or beige dorsum often with a contrasting broad mid-dorsal stripe of similar colors. It has a purplish or black venter with fine light speckling over the entire surface. This species will coil its body and tail when handled; it is fragile and easily injured.
Batrachoseps nigriventis looks similar to the related species
Batrachoseps pacificus and
Batrachoseps gabrieli. == Reproduction ==