Metaverruca defayeae Buckeridge, 1994

Figures 2 F, 23, 24

Metaverruca defayeae Buckeridge, 1994: 109, fig. 9. — Buckeridge, 1997: 138.

Material examined. CEL-BB-100, 4 specimens, Stn. CP371 (24º28.521’N, 122º12.821’E, 26 Aug. 2006, depth: 582–613 m), BD 10.22–13.10 mm.

Diagnosis. External shell smooth, with dense growth lines; movable tergum and scutum with 4 articular ribs; mandible with 5 teeth; caudal appendage short, <length of basal segment of pedicle of cirrus VI.

Description. Shell white, low conic, sides steep, surface smooth, with dense growth lines; basis membranous (Fig. 2 F); operculum sub-parallel to basis (Fig. 2 F); orifice D-shaped (Fig. 2 F); rostrum and carina articulated with up to 5 ribs (Fig. 2 F); fixed scutum with myophore; movable tergum quadrangular, strong apical basal rib and secondary 3 ribs interlocking with movable scutum; movable scutum triangular, articulating with movable tergum by 3 secondary ribs and 1 apico-basal rib. Maxilla bilobed, with dense setae (Fig. 23 A); maxillule notched, 2 large, cuspidate setae above notch, 6 cuspidate setae in notch,> 10 cuspidate setae below notch on expanded margin (Fig. 23 B); mandible with 4 main teeth, 2 small teeth representing fifth (Figs 23 C, G, E), lower margin hirsute, sharp spines and pectinations at inferior angle (Fig. 23 E); mandibular palps elongated, setae along superior margin (Fig. 23 D); labrum concave, with row of fine, small teeth (Figs 23 F, H). Cirrus I with rami unequal, outer ramus 21-segmented, inner ramus 12-segmented (Fig. 24 A); cirrus II with outer ramus longer, 19-segmented, inner ramus shorter, 13-segmented (Fig. 24 B); cirri III–VI similar; cirrus III with outer ramus 23-segmented, inner ramus 22-segmented; cirrus IV with outer ramus 27- segmented, inner ramus 28-segmented; cirrus VI with outer ramus 32-segmented, inner ramus 28-segmented (Fig. 24 C, D, E); caudal appendages short, 8-segmented, length <height of basal segment of pedicel of cirrus VI (Fig. 24 F).

Remarks. This is a new record for Taiwanese waters. Buckeridge (1994) concluded Metaverruca defayaea to be morphologically close to M. recta (Aurivillius, 1898) . The major difference between these two species is the number of interlocking ribs on the movable scutum and tergum; M. defayaea has 4 whilst M. recta has 3. In the present study, the fifth tooth of the mandible of M. defayaea is represented by 2 small teeth, whilst the fifth of M. defayaea in Buckeridge (1994) is represented by a single small tooth. The taxonomic status of M. defayaea in Taiwanese waters will need to be further evaluated from larger samples sizes and with support from a molecular approach.