122 



D.G. REID AND C. OSORIO 



showing external rayed pattern; head and tentacles dark grey to 

 black, sides of foot dark grey, densely mottled with white tubercles. 



Habitat. On rock and in crevices, from mid eulittoral Mytilus 

 zone to lowest eulittoral, on exposed coasts. Common in super- 

 ficially bare grazed zone between Mytilus zone above and calcareous 

 red algal zone of sublittoral fringe, on moderately exposed cliffs, 

 together with Nacella magellanica, Chiton granosus and Tegula 

 atra. This is an abundant species in southern Chile, reaching densi- 

 ties of 17 per m 2 in areas protected from humans (Jara & Moreno, 

 1984) and occurring in the mid to low eulittoral on both exposed and 

 sheltered coasts (Bretos, Gutierrez & Espinoza, 1988; Godoy & 

 Moreno, 1989). It is restricted to the intertidal zone (McLean, 1984). 



RECORDS. Stations 5, 9, 13, 14, 17. Elsewhere the species occurs 

 from Valparaiso to Tierra del Fuego, with overlap between the 

 nominate, southern subspecies and the northern F. p. lata Sowerby 

 on I. Chiloe (McLean, 1984). Total range: 33-56°S. 



Remarks. This species is the major herbivore of the mid and low 

 shore on exposed rocky coasts in southern Chile, grazing principally 

 on Iridaea. It is one of the main species in commercial limpet 

 catches. In the vicinity of human settlements, where collection 

 pressure on this species is strong, algae proliferate on the shore. 

 However, when humans were excluded from a shore near Valdivia 

 the density of F. picta increased to 3 per m 2 and algal cover was 

 reduced (Moreno & Jaramillo, 1983; Moreno, Sutherland & Jara, 

 1984; Duarte, Asencio & Moreno, 1996). On the more remote 

 shores of the present study area the density of F. picta remains high 

 in suitable habitats of moderate wave exposure, and grazing pres- 

 sure by this and other herbivores appears to result in a low eulittoral 

 zone without large macroalgae. 



Family TROCHIDAE 



Tegula (Chlorostoma) atra (Lesson, 1831) 

 (Figure 3J) 



Trochus ater Lesson, 1831: 344, pi. 16, fig. 2, 2'. 



Chlorostoma atra -Dell, 1971: 195 (synonymy). 



Tegula (Chlorostoma) atra - Marincovich, 1973: 24, fig. 42 (syn- 

 onymy). 



Tegulaatra-Osorio, Atria & Mann, 1979: 17-18, fig. 14.Castellanos 

 & Landoni, 1989: 27, pi. 4, fig. 4. 



Description. Shell to 39 by 41 mm (to 57 mm, Osorio et ai, 

 1979); trochoidal with rounded periphery; surface smooth; no um- 

 bilicus, blunt tooth at base of columella; colour dull purple black 

 above, apex often eroded, base whitish; interior nacreous. 



Habitat. Abundant on rocky shores of sheltered and moderate 

 exposure; on and under cobbles, boulders and on cliffs; mid to low 

 eulittoral, from Mytilus zone to zone of calcareous red algae in 

 sublittoral fringe, and an important herbivore of the bare, grazed belt 

 between these two zones on moderately exposed cliffs; rarely 

 sublittoral (one specimen from 7-9 m, station 22); rare at station 22 

 where salinity was recorded as 15— 21%o. In central and northern 

 Chile this species is typical of the Lessonia and Lithothamnion zone 

 of the sublittoral fringe, on sheltered and moderately exposed coasts 

 (Guiler, 1959a, b; Marincovich, 1973; Ruiz & Giampaoli, 1981). 



RECORDS. Stations 1, 5, 7, 8, 10, 12, 14, 15, 17, 20, 21, 22. 

 Elsewhere Pacasmayo (Peru) to Magellan Strait (Marincovich, 1 973). 

 Range: 7-54°S. 



Remarks. This is an edible species; the national harvest in 1997 

 was 159 tonnes (SERNAP, 1998). 



Diloma nigerrima (Gmelin, 1791) 

 (Figure 3E) 



Turbo nigerrimus Gmelin, 1791: 3597. 



Diloma nigerrima - Dell, 1971: 195-197, pi. 1, fig. 8, pi. 2, fig. 2 

 (synonymy). Marincovich, 1973: 23-24, fig. 45. Powell, 1979: 

 53. Castellanos & Landoni, 1989: 29, pi. 4, fig. 6. 



Description. Shell to 21 by 19 mm; turbinate; sculptured with 

 indistinct spiral grooves, stronger on spire whorls, strongest groove 

 just below suture; colour dull purple black, including base, apical 

 whorls often eroded to reveal nacre; interior nacreous. 



Habitat. Abundant in clusters beneath stones in upper eulittoral, 

 on moderately sheltered cobble and boulder shores. A similar 

 habitat was noted by Dell ( 1 97 1 ) and Brattstrom ( 1 990) on I. Chiloe, 

 with additional records from the mid and low eulittoral; in northern 

 Chile Marincovich (1973) recorded it in clusters in the lower 

 intertidal zone. 



RECORDS. Stations 7, 8. Elsewhere Salaverry (Peru) to Magellan 

 Strait (Marincovich, 1973). The same (Powell, 1979) or a closely 

 related species (Dell, 1971) occurs in New Zealand. Range: 8-54°S. 



Remarks. This species was found at only two stations, where it 

 was abundant and found at levels above those occupied by the 

 superficially similar Tegula atra. 



Margarella violacea (King & Broderip, 1832) 

 (Figure 3D) 



Margarita violacea King & Broderip, 1832: 346. Sowerby, 1838: 



24. 

 Photinula violacea -Strebel, 1905a: 145-152, pi. 5, figs 1-8, 12, 13. 

 Margarella violacea - Powell, 1951: 96. Deambrosi, 1969: 51-52, 



fig. 1 (radula). Dell, 1971: 194 (synonymy). Castellanos & 



Landoni, 1989: 16, pi. 3, fig. 4. 

 Promargarita violacea - Dell, 1990: 77-78. 



Description. Shell to 6.0 by 6.7 mm (to 10.3 by 1 1 .5 mm, Dell, 

 1971); trochoidal with rounded whorls, umbilicus minute or closed; 

 surface smooth, shining; colour iridescent violet pink, white around 

 umbilicus; interior nacreous; operculum corneous. 



Habitat. Dredged from 10-15 m depth, on substrates of cobbles 

 with encrusting calcareous red algae, silt with scattered pebbles and 

 shells, and shell gravel. Not common. In the original description it 

 was noted that this species is found on the fronds of Macrocystis in 

 the Magellan Strait (King & Broderip, 1832), and it has also been 

 recorded from both fronds (Dell, 1971; Castilla, 1985) and holdfasts 

 (Ojeda & Santelices, 1984) of kelp in the Beagle Channel; it was not 

 found on Macrocystis in our survey. Dell ( 1 97 1 ) recorded specimens 

 from the intertidal and to a depth of 12 m. 



RECORDS. Stations 7, 14, 25. Elsewhere Puerto Eden to Tierra del 

 Fuego, also Falkland Is (Dell, 1971), so that ours are the most 

 northerly records. Range: 46-55°S. 



REMARKS. Confusion surrounds the specific identification, generic 

 assignment and relationships of the Magellanic and Antarctic species 

 variously classified in Margarites, Margarita, Margarella and 

 Promargarita. The present specimens are smaller and have a slightly 

 lower rate of whorl expansion than the types of the species (NHM) 

 from the Magellan Strait, although shape is evidently variable 



