Notobranchaea tetrabranchiata

(Bonnevie, 1913)

Body opaque, visceral organs visible through body wall. Visceral mass not reaching caudal body pole. Skin smooth, unpigmented. Anterior tentacles small, greyish-green. Buccal cones absent. Posterior gill with 4 undulating but not fringed crests, which converge into a terminal knob. Head parts short and thick, no clear indication of a neck region. Foot composed of two lateral lobes with broad bases attached horizontally near neck region; and rather long, narrow pointed posterior lobe. Wings narrow at base, broadly truncated distally. Very shallow vestibulum and buccal cavity partly surrounded by thick circular muscles. Hooks short, robust, curved, hollow, pointed, about 14 in each sac. Hook sacs shallow with weakly developed musculature. With "clear cells" dorsal to hook sacs. Jaw composed of row of conical, somewhat triangular denticles, about 16 in number. Penis forms a broad folded lobe. Radula formula 6-1-6 or 5-1-5. Thirty transverse rows of teeth. Median plate semilunar, with 1 or 3 small central cusps and dentition on free border. Central cusps very small, represented by central group of denticles between two lateral groups. Body length 16 mm.

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