Chiton (Chiton) cumingsii , Frembly 1827

(FIGS 4C, 7A, B, 10, 11)

Chiton cumingsii Frembly, 1827: 198, suppl. pl. 16, fig. 3; Dall, 1919: 247. Chiton cumingsii: Reeve, 1847, pl. 1, figs 2a, b; Plate, 1902: 46, pl. 3, figs 179–184, pl. 4. Chiton cumingi: Pilsbry, 1893: 164, pl. 30, figs 29–31. Chiton (Amaurochiton) cumingsii: Bullock, 1988b: 166, figs 59–63, 69, 74 and 77. Chiton (Chiton) cumingsii: Kaas et al., 2006: 113, fig. 37, map 14 (bibliography and synonymy).

Type material: NHMUK 20190538 /1 (lectotype from the J. E. Gray collection, no locality data), NHMUK 20190538 /2 (paralectotype, teratological specimen), NHMUK 20190538 /3–4 (paralectotypes), all designated herein.

Type locality: Valparaiso, Chile, fide Frembly, 1927.

Descriptive notes: Size: animal up to 84 mm long and 40 mm width (Table 2). Colour: usually pink with black concentric lines compact (Fig. 4C), some individuals can be almost black; jugal area usually more vivid colour. Body shape: oval to elongated-oval, middle dorsal elevation. Slit formula: 12–15/1/10–16. Plates: intermediate plates separated by space not exposed mantle, slightly overlapping one over the other, lines of growth in intermediate plates apparent to the naked eye (Fig. 10). Intermediate plate with numerous aesthetes (Fig. 11E, F). Tail valve back straight (Fig. 10D). Apophyses: moderately short, connected by short jugal lamina, delicately denticulate, clearly triangular and trapezoidal intermediate valves in valve series (Fig. 10B, C, F). Perinotum: moderately broad, dorsally with imbricated, flat and triangular scales (Fig. 11A, C). Spicules at the ventral side of the perinotum (Fig. 11C). Radula: central tooth rounded and hooked. The major lateral rounded (Fig. 11B, D).

Distribution: We found this species from Lobitos (~ 4°S), Peru to Quellón (~ 43°S), Chile (Fig. 1). It was

previously reported from Paita (~ 5°S), Peru to Puerto Montt (~ 41°S), Chile (Marincovich, 1973).

Remarks: This species is easy to differentiate from all other Chiton species in the area by their high number of ribs in all plates with small grains. In the head valve, they have more than 40 ribs of grains. This species has been introduced in the Canary Islands (28°06’N, 15°25’W) (Arias & Anadón 2013).

Notes on designation of type material: The lectotype and paralectotype material comprise a single lot in the collections of the Natural History Museum, London (NHMUK) (Fig. 6). It is probable that some of Frembly’s specimens were deposited in the NHMUK via the collections of contemporaries, such as Hugh Cuming and J. E. Gray, although there is nothing to link any of this early material to Frembly directly (T. S. White, pers. comm). Type material for other species described by Frembly has also been attributed to the NHMUK collection (Kaas et al., 2006; Bullock, 1988b), although the status of these specimens requires further careful investigation. In the original description of Chiton cumingsii, Frembly (1827: 199) noted ‘A specimen also was found [showing]... only seven valves, but inside the articulation of the other valve was plainly seen’. Chiton teratologies are rare (Torres et al., 2018). There was only one teratological specimen of this species in the NHMUK collection, amongst a lot of four specimens (NHMUKMUK 20190538/1–4) from the J. E. Gray Frembly (1927) (Fig. 7B). The specimen closest to the potentially generalized dimensions given in Frembly’s original description (‘length two inches, breadth 1 3/10’; 5.0 × 3.3 cm) has been designated the primary lectotype (NHMUK 20190538/1, dimensions, 4.2 × 2.3 cm).