120 



Description. Shell 5.5 by 4.0 mm, height 3.5 mm (to 16 mm in 

 length, Powell, 1951); tall cap-shaped with coiled apex; short longi- 

 tudinal slit just anterior to shell apex; sculpture of 25 radial ribs 

 made scaly by growth lines, with a smaller riblet in each interspace; 

 white. 



Habitat. Single dead shell dredged in 10-15 m, on substrate of 

 cobbles encrusted with calcareous red algae, near shore in sheltered 

 bay. Dell (1971) recorded the species from 6-20 m in southern 

 Chile, Powell (1951) from 60-342 m, and Dell (1990) to 2804 m in 

 the Ross Sea (if the synonymy with P. spirigera is accepted). 



RECORDS. Station 7 (single dead shell). Elsewhere I. Chiloe (Dell, 

 1971) to Magellan Strait, also Falkland Is (Powell, 1951) and 

 perhaps circum-Antarctic (Dell, 1990). Range: 42-75°S. 



Remarks. The taxonomy of the southern species of P. ( Puncturella) 

 is unclear, and critical revision is required (Dell, 1990). They are 

 closely similar to P. (P.) noachina (Linnaeus, 1771) from the north- 

 ern Pacific and Atlantic Oceans, but are usually regarded as 

 specifically distinct. The single shell found has been compared with 

 the holotype (NHM) from the Falkland Islands, and closely resembles 

 it in size and sculpture, although slightly less acutely conical. 

 Previous authors differ in the number of species recognized in this 

 group, according to their interpretation of differences in shell shape 

 and degrees of sculpture. However, in view of the intraspecific 

 variation in these features described in South African specimens by 

 Herbert & Kilburn (1985), it is possible that only a single species 

 may be involved. 



Fissurella (Fissurella) nigra Lesson, 1 83 1 



(Figure 3A) 



Fissurella nigra Lesson, 1831: 4 1 2^4 1 3 . Osorio, Atria & Mann, 

 1979: 17, fig. 13. Castellanos & Landoni, 1988: 15, pi. 2, fig. 5. 

 Oliva & Castilla, 1992: fig. 9. 



Fissurella (Fissurella) nigra - McLean, 1984: 52-55, figs 200-21 1 

 (synonymy). 



Description. Shell to 104 by 75 mm, height 40 mm (maximum 

 length 140 mm, Bretos,Quintana& Ibarrola, 1988); outline elongate 

 oval, narrowed anteriorly, base resting flat, foramen slightly anterior 

 of centre; sculpture almost smooth in large shells, except for concen- 

 tric growth lines, but with numerous fine radial ribs in juveniles; 

 colour purple-black, foramen outlined in white (eroded to reveal 

 inner aragonitic shell layer); interior white, margin (external calcitic 

 layer) of outer black and inner translucent gray zone; head and 

 tentacles black, sides of foot dark grey to black, with a row of small 

 white tubercles. 



Habitat. Common beneath rocks on sheltered and moderately 

 sheltered boulder and rocky shores, in mid to low eulittoral zone. Fre- 

 quently in groups of up to 7 individuals under a single rock. A similar 

 habitat was reported by McLean ( 1 984), but it can also be found in the 

 immediate subtidal zone (Bretos, Quintana & Ibarrola, 1988). 



Records. Stations 1, 7, 14, 15, 20, 21. Elsewhere Valparaiso to I. 

 Navarino (McLean, 1984). Range: 33-55°S. 



Remarks. All the Chilean Fissurella species are edible, and the 



D.G. REID AND C. OSORIO 

 total extraction for 1997 was 3063 tonnes (SERNAP, 1998). 



Fissurella (Fissurella) oriens oriens Sowerby, 1835 

 (Figure 3C) 



Fissurella oriens Sowerby, 1835: 124. 



Fissurella (Fissurella) oriens oriens - McLean, 1984: 49-52, figs 



178-199 (synonymy). 

 Fissurella oriens oriens - Castellanos & Landoni, 1988: 14, pi. 2, 



figs 10, 11. 



Description. Shell to 54 by 30 mm, height 12 mm (maximum 

 length 70 mm, McLean, 1984); outline more or less narrowly oval, 

 narrowed anteriorly, either sides or ends of shell slightly raised when 

 on flat surface, foramen almost central; sculpture smooth, or with 

 very fine indistinct striae in young shells; colour variable, white to 

 pink, often with broad purple grey rays (not divided into lines), but 

 pattern may be absent; interior white with narrow translucent mar- 

 gin; animal pale, head grey, sides of foot mottled pink and grey, 

 tentacles and mantle margin yellowish. 



Habitat. Under rocks and in rock pools, in lowest eulittoral, on 

 moderately sheltered and moderately exposed shores; juveniles 

 found in holdfasts and on fronds of Macrocystis, 10-15 m depth. 

 Unidentified fissurellids made up the major molluscan component 

 of the invertebrate biomass associated with Macrocystis holdfasts in 

 the Beagle Channel (Ojeda & Santelices, 1984). McLean (1984) 

 recorded this species from the lower intertidal to 30 m depth. 



RECORDS. Stations 1, 5, 9, 14, 17. Elsewhere Valparaiso to Tierra 

 del Fuego, of which specimens north of about 37°S belong to the 

 subspecies F. o. fulvescens Sowerby (McLean, 1984). Total range: 

 33-56°S. 



Remarks. This species is distinguished from the similar F. picta 

 by its lack of radial ribs and by its paler, yellowish animal, and 

 occupies a lower and more sheltered habitat. According to the 

 detailed monograph of the Magellanic species of Fissurella by 

 McLean (1984), an additional species, F. radiosa Lesson, 1831, 

 occurs in the region and, although similar to F. oriens, can be 

 distinguished by its strong radial ribs. 



Fissurella (Fissurella) picta picta (Gmelin, 1791) 

 (Figure 3B) 



Patella picta Gmelin, 1791: 3729. 



Fissurella (Fissurella) picta picta - McLean, 1984: 37-43, figs 



123-146 (synonymy). 

 Fissurella picta -Osorio, Atria & Mann, 1979: 16, fig. 1 1 . Castellanos 



& Landoni, 1988: 1, pi. 2, figs 3, 4. Oliva & Castilla, 1992: fig. 3. 



Description. Shell to 88 by 56 mm, height 32 mm; outline 

 narrowly oval, narrowed anteriorly, sides slightly raised when on 

 flat surface, foramen slightly anterior of centre; sculpture of sharp 

 narrow ribs of varying size, and irregular concentric growth lines; 

 colour white to grey, with broad purple-black rays, each divided into 

 several dark lines; interior white, margin (external calcitic layer) 



Fig. 3 A. Fissurella (Fissurella) nigra (76 mm). B. Fissurella (Fissurella) picta picta (60 mm). C. Fissurella (Fissurella) oriens oriens (53 mm). 

 D. Margarella violacea (7.1 mm). E. Diloma nigerrima (18 mm). F, G. Crepidula dilatata (sensu lato) (72 mm). H, I. Trochita trochifonnis (54 mm). 

 J. Tegula (Chlorostoma) atra (30 mm). K. Acanthina monodon (form monodon from exposed shore at station 14; 46 mm). L. Acanthina monodon (form 

 unicornis from sheltered shore at station 1; 57 mm). M. Argobuccinum (Argobuccinum) pustidosum ranelliforme (78 mm). N. Trophon plicatus (51 mm). 

 O. Concholepas concholepas (94 mm). (All specimens from study area; NHM collection). 



