Diagnosed by having two dorsal fins connected at the base, oral disc narrower than head, usually blunt disc teeth, 2 supraoral teeth, usually 2-2-2 lateral circumoral teeth, usually 20-24 posterior circumoral teeth, usually 7-8 infraoral teeth, usually 67-73 trunk myomeres. Coloration with lead gray to slate blue above, white or silver white below, yellow fins, dark gray to black blotch on caudal fin, no black on lateral-line pores and breeding adult is olive green or pink-purple to shiny black above, and black stripe at base of dorsal fins (Ref. 86798). Other adult diagnostic features: 10.3-21.7 (exceptionally, 26.0-35.4) cm TL and wet weight 2.8-16.2 g. Body proportions, as percentage of TL (based on 329 specimens measuring 10.3-21.7 cm TL): prebranchial length, 10.4-13.7; branchial length, 9.0-11.9; trunk length, 46.7-53.5; tail length, 24.0-32.3; eye length, 1.2-2.6; disc length, 3.2-6.0. Urogenital papilla length, as a percentage of branchial length, in 44 spawning males measuring 14.6-21.4 cm TL, 4.5-16.7. Trunk myomeres, 64-74. Dentition: supraoral lamina, 2 unicuspid teeth, but occasionally a third small cusp is present on the bridge; infraoral lamina, 6-10 unicuspid teeth; 3 endolaterals on each side; endolateral formula, typically 2-2-2; 3 rows of anterials; first row of anterials, 4-6 unicuspid teeth; exolaterals usually absent, (Kott (1974) reported on the presence of 1-2 exolaterals, on either or both lateral fields in 21% of specimens examined); single row of posterials with 20 unicuspid teeth; transverse lingual lamina u-shaped with 15 unicuspid teeth, the median one greatly enlarged; longitudinal lingual laminae each with 5-8 unicuspid teeth. Marginal membrane vestigial. A small gular pouch occurs in males. Velar tentacles, 5-9, with tubercles. Body coloration (preserved), uniformly slate brown on the dorsal aspect, progressively paler on the lateral aspects, and much paler on the ventral aspect. Lateral line neuromasts darkly pigmented, at least the ventral ones. Gular region darkly pigmented. Second dorsal fin with a dark blotch near the apex (38% of individuals) or not (62%). Extent of caudal fin pigmentation, 1% to <25% (44% of specimens), 25% to <75% (26%) or, 75% or more (30%). Caudal fin shape, spade-like. Oral papillae, 18-35 (Ref. 89241).