“Philobrya capillata sp.n. (pl. IV, 4, 5, 9 ; see p. 164, fig. 2, nos. 5, 8, 9)
OCCURRENCE : St. 160, Shag Rocks, South Georgia, 177 m (type); St. 190, Palmer Archipelago, 93-130 m; WS 840, Falkland Islands, 368-463 m, paratype.
DISTRIBUTION: Shag Rocks; Falkland Islands; Palmer Archipelago.
Shell large for the genus, narrowly ‘pinctadoid ' in form, with a short, sloping anterior wing, posterior margin constricted. Prodissoconch with flanged margin, central area swollen, surface punctate, lateral areas with microscopic divaricating radials, margin ornamented with many fine punctations. Rest of shell covered with a fine periostracum. Periostracum sculptured with 36 radial ridges crossed by concentric flanges, drawn out at intersections into fine, sharp-pointed, hair-like processes. Shell surface beneath periostractum apparently sculptured with low radials. Ligament comparatively long, flanked anteriorly by an elongate, vertically striated area and a small striate boss at the apex of the anterior margin. Anterior, ventral and posteroventral margins broadly crenulated.
In the type-specimen the mantle-edge bears no eye-spots. In the same specimen there were some 400 young shells attached to the gills. The animal is attached by a short, rather coarse byssus.
Length (mm)
Height (mm)
Inflation
St. 160 (holotype)
8.0
10.0
2.8 (single valve)
St. 190 (paratype)
7.2
9.2
5.1 (double valves)
WS 840
7.1
9.6
3.0 (single valve)
Holotype, B.M. Reg. no. 1962867/1, St. 160, and paratype, B.M. Reg. no. 1962868/1, St. WS 840, in British Museum (Natural History).
The closed specimen from St. 190 agrees well with the type, being clothed in a similar epidermis. The specimen from WS 840 consists of two associated valves, clean of epidermis. These agree very well in outline except that the anterior wing is less pronounced, the dorsal and anterior margins forming a single, regular, curve. The sculpture of the actual shell surface consists of some 24 broad, low, radial ribs. The prodissoconch is somewhat worn but appears to have a regularly concave surface with traces of divaricating radials. This latter specimen is associated provisionally with P. capillata sp.n., but more material may show that the differences observed are constant, in which case it would probably merit specific separation.
P. capillata sp.n. seems closest in general appearance to P. tumida (Thiele, 1912). This latter species is, however, described as having short hairs with a peculiar apical head, on the periostracum. It does not appear to have been re-collected, and it is possible that these hairs were due to some encrusting organism. Even discounting this feature, P. tumida may be differentiated from P. capillata by the more numerous radiating ribs. P. capillata is probably also related to P. barbata Thiele, 1912, described from Kerguelen.”
(Dell, 1964: 170)
