116 



D.G. REID AND C. OSORIO 



Chiton bowenii King & Broderip, 1832: 338-339. Kaas & Van 



Belle, 1998: 34. 

 Chiton (Amaurochiton) magnificus bowenii - Bullock, 1988:165- 



166, figs 55, 56, 71, 76 (synonymy). 

 Chiton latus Sowerby, 1825 - Leloup, 1956: 50-54, figs 26, 27 



(includes nominate subspecies). 



Description. Valve area to 46 by 24 mm, maximum width of girdle 

 5 mm (total length up to 86 mm, Bullock, 1988); valves flattened to 

 carinate, glossy ; jugal and pleural areas smooth; lateral triangles, head 

 and tail valves with indistinct radiating ribs; shell colour entirely 

 black, dark red, orange-pink or blue-grey, often with strong pattern of 

 longitudinal streaks on central region and radial streaks on lateral 

 triangles; girdle black, red or brown, with large, glossy, imbricating 

 scales, the innermost one third of the width of the girdle with slightly 

 smaller and narrower scales than the rest (Fig. 6F). 



Habitat. Common under rocks in lower eulittoral ; small juveniles 

 dredged on cobbles at 10-15 m depth; moderately sheltered to 

 exposed coasts. Leloup (1956; as C. latus) recorded the species both 

 intertidally and to 2-5 m depth, and Dell (1971; as C latus) 

 mentioned a maximum depth of 13 m. In central Chile the typical 

 subspecies inhabits pools and boulder fields from high to low tide, is 

 larger and more common in exposed localities, but absent from rock 

 walls (Otaiza & Santelices, 1985; as C. latus). 



Records. Stations 1, 5, 7, 12, 14, 15, 17. Elsewhere I. Chiloe, 

 Magellan Str. and Tierra del Fuego (43-53°S); typical subspecies I. 

 San Lorenzo (Peru) to I. Chiloe (Bullock, 1988) (12-43°S). Total 

 range of species: 12-53°S. 



REMARKS. Bullock (1988) distinguished C. m. bowenii from the 

 typical northern subspecies by its smooth sculpture, more carinate 

 valves, more elongate outline, brighter coloration and smaller girdle 

 scales. He noted the 'nearly complete geographical isolation of the 

 two', although this is probably a sampling artefact. In Isla Chiloe he 

 reported that both types could be found, together with intermediates, 

 and this appears to question the validity of the subspecific distinc- 

 tion. The present material shares the smooth sculpture, small scales 

 and frequently bright coloration of the southern form, but the valve 

 profile and outline are more variable. Additional material is required 

 to determine whether the subspecies are indeed distinct entities, or if 

 there is a latitudinal cline. The synonymy of the nominate subspe- 

 cies is complex, and includes C. striatus Barnes, 1824, C. latus 

 Sowerby, 1825, C. olivaceus Frembly, 1827 and C subfuscus 

 Sowerby, 1832 (see Bullock, 1988). Small specimens could be 

 confused with Ischnochiton pusio. 



Chiton (Chondroplax) granosus Frembly, 1 827 

 (Figure 2J) 



Chiton granosus Frembly, 1827: 200-201. Leloup, 1956: 48-50, 

 figs 24, 25. Marincovich, 1973: 43, fig. 98. Osorio, Atria & Mann, 

 1979: 13, fig. 5. Kaas & Van Belle, 1998: 84. 



Chiton (Chondroplax) granosus -Bullock, 1988: 185-187, figs 96, 

 97, 103, 140, 141, 143, 144. 



Description. Valve area to 44 by 25 mm, maximum width of 

 girdle 7 mm (total length up to 80 mm, Osorio et al., 1979); central 



area with longitudinal striations; lateral triangles, head and tail 

 valves with radiating rows of coarse nodules; valves usually eroded 

 so that sculpture is not visible; shell colour dark brown to black, with 

 broad longitudinal pale stripe on either side of jugal tract, striking 

 even in eroded specimens; girdle with coarse black scales. 



Habitat. In wave-surge gullies and crevices, and on cliffs, in 

 lower eulittoral, on exposed shores. This species is abundant in 

 southern, central and northern Chile, mainly on exposed cliffs in the 

 mid to low intertidal zone (Jara & Moreno, 1 984; Otaiza & Santelices, 

 1985; Brattstrom, 1990), although it has also been reported from the 

 undersides of rocks (Leloup, 1956; Marincovich, 1973) and at the 

 high tide level (Frembly, 1827; Leloup, 1956; Brattstrom, 1990). 



RECORDS. Stations 12, 13, 17. This extends the known range of 

 Tumbes (Peru) to I. Chiloe (Bullock, 1988). Range: 12-46°S. 



Remarks. This species was found infrequently in the Estero 

 Elefantes, and then only on the most wave-exposed of the sites 

 visited. Moreno & Jaramillo ( 1983) reported that the main food of C. 

 granosus is barnacle larvae. 



Tonicia atrata (Sowerby, 1840) 



(Figure 2K) 



Chiton atratus Sowerby, 1840: 294. 



Tonicia atrata -Leloup, 1956: 59-67, figs 31-35 (synonymy). Kaas 

 & Van Belle, 1998: 25 (synonymy). 



Description. Valve area to 85 by 30 mm, maximum width of 

 girdle 13 mm; jugal area with deep longitudinal striae; lateral 

 triangles not distinct; entire surface with fine, regular granulation 

 (not evident in large, eroded specimens); mucro of tail valve almost 

 central, post-mucronal slope convex; shell colour purplish black, 

 beaks often pale pink, some specimens with fine concentric lines 

 and irregular radial rays; girdle macroscopically smooth, with mi- 

 croscopic spicules, flesh pink. 



Habitat. Under stones and in pools, in lower eulittoral, on shel- 

 tered and moderately sheltered shores. Leloup ( 1 956) and Brattstrom 

 (1990) also recorded this species from the mid and low eulittoral, 

 and Dell (1971) down to a depth of 10 m. 



RECORDS. Stations 1, 5, 7, 12, 14, 15, 20. Elsewhere Puerto Montt 

 to Tierra del Fuego (Leloup, 1956; Dell, 1971). Range: 40-54°S. 



Remarks. Leloup (1956) described the variation in valve form 

 and sculpture in this species; the present specimens correspond with 

 his figures of the synonymous T. fasti giata (Sowerby, 1843). 



Tonicia chilensis (Frembly, 1827) 



(Figure 2E) 



Chiton chilensis Frembly, 1827: 204-205. 



Tonicia chilensis - Kaas & Van Belle, 1998: 45 (synonymy). 



Tonicia elegans (Frembly, 1827) - Leloup, 1956: 69-77, figs 38^16. 



Description. Valve area to 37 by 15 mm, maximum width of 

 girdle 6 mm (total length up to 70 mm, Kaas & Van Belle, unpubl.); 

 jugal area with a few longitudinal striae, elsewhere almost smooth; 



Fig. 2 A. Chaetopleura (Chaetopleura) peruviana (44 mm). B. Plaxiphora (Plaxiphora) aurata (42 mm). C. Chiton (Amaurochiton) magnificus bowenii 

 (40 mm). D. Ischnochiton (Haploplax) pusio (14 mm). E. Tonicia chilensis (20 mm). F, G. Scurria parasitica (15 mm). H, I. Scurria ceciliana (19 mm). 

 J. Chiton (Chondroplax) granosus (43 mm). K. Tonicia atrata (36 mm). L, M. Nacella (Patinigera) magellanica (typical form; 40 mm). N, O. Nacella 

 (Parinigera) magellanica (form venosa; 37 mm). P, Q. Nacella (Nacella) mytilina (32 mm). (All specimens from study area; NHM collection). 



