“Nuttallochiton mirandus (Smith MS, Thiele, 1906)
(Fig. 53. Map 24)
Type: ZMHU.
Type locality: East of Bouvet Island.
Notochiton mirandus Smith MS, Thiele, 1906: 332, pl. 29: figs 11-16; Odhner, 1923a: 2; Ashby, 1929d: 225, pl. 24: figs 4-5, 6a-b.
Nuttalochiton (sic!) mirandus; Dell, 1964a: 119 (bibliography); Leloup, 1966: 2, figs 1-3, pl. 1; Arnaud, 1974a: 554; 1974b: 641; Ferreira, 1980: 59.
Description. Animal of very large size, saw-toothed in lateral view, holotype 80 × 35 mm (Cotton, 1937: 14), elongate oval, somewhat narrowing at the level of valves VII and VIII, highly elevated (dorsal elevation c. 0.52), carinated, side slopes straight, valves relatively brittle, not beaked. Colour of tegmentum creamy white, with some valves, or large parts of it, reddish brown.
Head valve more than semicircular, almost as wide as intermediate valves, anterior slope slightly concave, posterior margin V-shaped, notched in the middle, tegmentum sculptured with 8-10 strong, radiating ribs, the interspaces finely radially grooved, growth lines weakly indicated. Intermediate valves with anterior margin sinuate, concave in the jugal area, convex at the pleurae which are somewhat posteriorly directed towards the sides, side margins wavy, posterior margin slightly convex at both sides of the inconspicuous apex, jugal axis weakly concave, lateral areas moderately raised, sculptured like head valve, 1 radial rib situated in the centre of the area, central area sculptured with numerous fine riblets, somewhat stronger than those on the lateral areas, radiating from the apex, some of them irregularly ornamented with minute pustules, jugum almost smooth. Tail valve pentagonal, longer than wide, considerably less wide than head valve, anterior margin convex at both sides of the somewhat forwardly produced jugal part, mucro at two thirds of the valve's length, sharply pointed though not elevated, antemucronal area sculptured with closely packed, radiating riblets, sometimes some of them ornamented with minute roundish or oval pustules, postmucronal area with up to 8 major radial ribs and odd interstitials, in some specimens the posterior margin is slightly concave in the central part.
Articulamentum white, apophyses large, rounded, continuous across the jugum, sinus deep though not reaching the anterior margin of the tegmentum, insertion plates strongly developed, slit formula 8-10/1/5-8 (Vayssière, 1917, fig. 4 represents a tail valve with 12 slits), slits deep, corresponding in position to the radial ribs of the tegmentum, teeth inequidistant, weakly grooved on the outside, slightly thickened at the edges of the slits.
Girdle rather wide, narrowing posteriorly, dull brown, dorsally covered with elongate, straight, finely striated, sharply pointed, brownish spicules, 160 × 38 µm, slightly longer along the margin, interspersed with solitary or grouped, white, long, smooth, straight or slightly curved, sharply pointed needles, up to 800 µm long, 44 µm thick. Ventrally the girdle is beset with whitish spicules of the same form and size as the dorsal ones. Thiele (1906: 332) mentioned, and figured, a posterior notch in the girdle, Leloup (1966: 4) expressly states that fresh, well extended specimens do not show that peculiarity.
Central tooth of radula hexagonal, with a rather thick blade, first lateral tooth about the same length, slightly wing-shaped, no blade, major lateral with tricuspid head, denticles more or less pointed, the central one much longer than the others.
Gills holobranchial, abanal, 40 (Cotton, 1937: 15) to 50 (Thiele, 1906: 333) ctenidia per side.
Distribution. N. mirandus is a rather commonly distributed antarctic, circumpolar deep-sea species, living in depths from 93 to 640 m.”
(Kaas & Van Belle, 1988: 122-124)
