Tubercles on sides of tail with extremely long spines. Small tubercles on ventral surface of disk, widely spaced so skin seems naked. In larger specimens, tubercles are sometimes truly absent. Except for 2 short longitudinal rows of tubercles anterior to the anal fin base, the principal tubercles occupy most of the ventral surface of tail; tubercles in skin covering bases of principal tubercles absent. Cephalic lateral-line counts: subopercular 5-6 (usually 5), preopercular, 2-3 (usually 2). Tail lateral-line counts 8-13. Fin-rays without tubercles, except sometimes a few found at the pectoral base. Pectoral fins slender. Pelvic fins with thickened skin on rays (Ref. 40826).