There are a pair of large kidney-shaped electric organs at the base of the pectoral fins, visible through the skin. The nostrils are placed just forward of the mouth and are connected to it by a broad nasoral groove the nasal flaps are long and fused into a central nasal curtain that overlaps the mouth. The mouth is straight, very narrow, and not highly protrusible, with strong labial folds and a weak groove around the periphery. This distinguishes the narkids from the family Narcinidae, which have somewhat longer snouts supported by broad rostral cartilages. The snout is moderately elongate and broadly rounded, with the rostral cartilage reduced to a slender medial rod. They have naked skin, without dermal denticles or thorns. Adult sleeper rays range in size from 8 to 46 cm in length and have flattened oval, circular, or pear-shaped pectoral fin discs.
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