MOLLUSCA OF SOUTHERN CHILE 



113 



Venus antiqua, Tagelus dombeii and Ensis macha were recorded. On 

 muddy shores of intermediate salinity the bivalve Mulinia edulis 

 was frequent (station 20). 



Dredging to a depth of 15 m in the Estero Elefantes (stations 1,9, 

 14, 22) yielded the most diverse molluscan assemblage encountered 

 during the entire survey, although numbers of individuals were 

 always low. The 25 species found were Chiton magnificus, Tonicia 

 chilensis, Ischnochiton pusio, Leptochiton medinae, Puncturella 

 conica, Iothia coppingeri, Margarella violacea, Homalopoma 

 cunninghami, Crepidula dilatata, Xymenopsis muriciformis, X. sub- 

 nodosus, Pareuthria powelli, Glypteuthria meridionalis, Nassarius 

 gayii, Adelomelon ancilla, Nuculapisum, Zygochlamys patagonica, 

 Felaniella inconspicua, Carditella tegulata, Carditopsis flabellum, 

 Cumingia mutica, Venus antiqua, Retrotapes exalbidus, Tawera 

 gayi and Mate I la solida. 



Much of the shore of the Estero Elefantes was fringed by exten- 

 sive beds of the giant kelp, Macrocystis pyrifera (sampled at stations 

 1, 7, 14, 22), growing from depths of about 10 m. In fully marine 

 situations the laminae of the kelp supported occasional animals of 

 Nacella mytilina and Flabellina falklandica, while in the holdfasts 

 were found Fissurella oriens and Aulacomya atra. In conditions of 

 lower salinity in the southern part of the Estero (station 22) the 

 species Leptochiton medinae, Plaxiphora aurata, Aulacomya atra 

 and Hiatella solida were present in the holdfasts. 



MATERIAL AND METHODS 



The majority of the material was collected during intertidal surveys. 

 Sampling was by general collecting and by quantitative transect 

 methods (the results of which will be reported elsewhere). A limited 

 amount of dredging was carried out in depths of up to 15 m, using a 

 small handmade apparatus (aperture 70 by 15 cm, with sacking 

 attached) dragged behind an inflatable boat. Plants of the giant kelp 

 Macrocystis were pulled up from depths of up to 10 m, and both 

 holdfasts and laminae examined for molluscs. Searches for 

 micromolluscs were made by washing dredged and hand-collected 

 samples of algae in freshwater, and also by close examination of 

 dredged sediments. Strandlines were searched for dead shells but, 

 unless otherwise noted, all records refer to living specimens. Collec- 

 tions and observations were made at a total of 26 stations (Table 1, 

 Figure 1). Surface salinity and temperature were noted. Material 

 was preserved in 10% seawater formalin and later transferred to 

 80% ethanol for storage. Duplicate collections are deposited in both 

 the Natural History Museum, London (NHM) and the Museo 

 Nacional de Historia Natural, Santiago (MNHNS). All figured 

 material is in the NHM; registered specimens carry the prefix 

 'BMNH'. 



In the Systematic Descriptions an abbreviated synonymy is given 

 for each species. This includes the reference to the original descrip- 

 tion, one or more references to the most recent taxonomic accounts 

 that can be consulted for complete synonymies, and significant recent 

 systematic works. References to the key works on the molluscs of the 

 region (Leloup, 1956; Soot-Ryen, 1959; Osorio & Bahamonde, 

 1970; Dell, 1971; Marincovich, 1973) are provided for all species. 

 Where previous authors have used names other than the ones we 

 consider to be valid, these are usually synonyms; cases of misidenti- 

 fication are indicated by 'not' followed by the original authority of 

 the name. The descriptions and dimensions of shells are based on the 

 present material, with additions from other sources as noted. Dimen- 

 sions are the greatest linear dimension of the shell, unless otherwise 

 indicated. All figured specimens are from this survey, except for three 



species in which the material was too fragmentary, in which case 

 specimens from the collection of the NHM have been substituted, as 

 noted. The designation of zones on the shore follows that of Lewis 

 ( 1 964). Records of geographical distribution refer only to the Chilean 

 coast, as far south as Cape Horn, including the Magellan Strait, Tierra 

 del Fuego and the Beagle Channel. 



SYSTEMATIC DESCRIPTIONS 



Class Polyplacophora 



Family LEPTOCHITONIDAE 



Leptochiton (Leptochiton) medinae (Plate, 1899) 

 (Figure 6A, C) 



Lepidopleurus medinae Plate, 1899: 82-89, pi. 5, figs 204-206. 



Leloup, 1956: 13-15, fig. 2. 

 Leptochiton medinae - Kaas & Van Belle, 1998: 122. 

 Leptochiton (Leptochiton) medinae - Kass & Van Belle, 1985: 80- 



83, fig. 35, map 37 (synonymy). 



Description. Valve area to 10.0 by 6.0 mm, maximum width of 

 girdle 1.1 mm; valves sculptured with numerous fine rows of small 

 granules, arranged longitudinally on central areas, radially on lateral 

 triangles and terminal valves; shell colour cream, often stained with 

 black deposits; girdle fawn, covered with minute, longitudinally 

 grooved, conical spicules (Fig. 6C); gills restricted to posterior part 

 of pallial groove (merobranchial). 



Habitat. Commonly dredged from 3-15 m; in Macrocystis 

 holdfasts; on cobbles encrusted with calcareous red algae; on peb- 

 bles and shells lying on silt; at salinities down to 15-22%c. This has 

 been recorded as a common sublittoral species in 15-30 m (Dell, 

 1971; Kaas & Van Belle, 1985), and to a depth of 250-300 m 

 (Leloup, 1956); Dell (1971) also noted one collection from the 

 intertidal Iridaea zone. 



Records. Stations 7, 22, 25. Elsewhere Puerto Montt to Tierra del 

 Fuego and Magellan Strait (Leloup, 1956; Kaas & Van Belle, 1985). 

 Range: 40-56°S. 



Remarks. This species should not be confused with the similarly 

 small, cream species Ischnochiton stramineus, which possesses 

 slitted insertion plates, quincuncial (not longitudinal) granular sculp- 

 ture and holobranchial gills. 



Family ISCHNOCHITONIDAE 



Chaetopleura (Chaetopleura) peruviana (Lamarck, 1819) 



(Figure 2A) 



Chiton peruvianus Lamarck, 1819: part 1: 321. 



Chaetopleura peruviana - Leloup, 1956: 37^10, figs 18-20. Dall, 



1971: 218. Marincovich, 1973: 43-44, fig. 101. Ferreira, 1983: 



220-221. Kaas & Van Belle, 1998: 142-143. 

 Chaetopleura (Chaetopleura) peruviana - Kaas & Van Belle, 1987: 



62-64, fig 27, map 1 1 (synonymy). 



Description. Valve area to 49 by 22 mm, maximum width of 

 girdle 11 mm; valves relatively flattened; valves sculptured with 

 radiating rows of fine pustules; shell colour marbled olive brown, 



