Sibogasyrinx archibenthalis (Powell, 1969)

Fig. 3R–T

Leucosyrinx (Sibogasyrinx) archibenthalis Powell, 1969: 344, pl. 264 figs 6–7.

Material examined

Holotype PHILIPPINES • Mindanao I., Iligan Bay, Tabu Point; 08°16′45″ N, 124°02′49″ E; depth 924 m; R/V Albatross, stn 5513; USNM 238773.

Description

MEASUREMENTS (holotype). SL 41.8 mm.

SHELL. Fusiform, narrow, with high, very narrow, flat-sided spire and relatively short, almost straight, un-notched siphonal canal. Protoconch small, globose, of 1.5 smooth whorls. Teleoconch of 12 whorls. Spire whorl profile quite straight and descending steeply to a narrowly rounded, flange-like, peripheral carina, abutting lower suture. Last whorl distinctly angled by peripheral carina, and base rapidly contracting toward moderately long anterior canal. Axial sculpture of rounded peripheral nodules, about 13 per whorl, but these become obsolete on last two whorls; subsutural nodules or folds lacking. Spiral sculpture of dense well defined and regular spiral cords, 11–12 on subsutural ramp. Anal sinus moderately deep, subsutural, broadly arcuate, confluent with large forward extension of outer lip. Colour opaque white, covered by a thin pale buff periostracum.

Remarks

The species is known only from the holotype. In shell shape it is most similar to S. pyramidalis. The differences are most obvious when comparing specimens of the same size (e.g., Fig.3 D–F and 3R); the last whorl is lower and the canal is proportionally much shorter in S. archibenthalis, while the spiral cords on the subsutural ramp are more pronounced and are of the same strength as on the remaining part of the last whorl. The last whorl is more angular in S. archibenthalis and the shell has a higher number of teleoconch whorls; in the holotype of S. archibenthalis the number of teleoconch whorls is 12 (SL 43 mm), compared with 9.5 (SL 46.8 mm) in samples of S. cf. pyramidalis 1 from the Philippines of similar shell size. Therefore, at present we consider S. archibenthalis to be a valid species.