SYSTEMATIC 99 



Margarella (Promargarita) tropidophoroides (Strebel) 



Promargarita tropidophoroides Strebel, 1908, p. 74, pi. 5, fig. 73«-</. 

 Promargarita tropidophoroides Thiele, 1912, pi. 15, fig. 17 (radula). 

 Margarella {Promargarita) tropidophoroides L. David, 1934, p. 127. 



Dentition. Fig. G, 4, p. 189. 

 Type locality. South Georgia, 20 m. 

 St. 1941. Leith Harbour, South Georgia, 29 Dec. 1936, 55-22 m. 

 St. MS 6. East Cumberland Bay, \ mile south of Hope Point to i\ cables S x E of King Edward Lt., South 



Georgia, 12 Feb. 1925, 24-30 m. 

 St. MS 10. East Cumberland Bay, \ mile south-east of Hope Point to \ mile south of Government Flagstaff, 



South Georgia, 14 Feb. 1925, 26-18 m. 

 St. MS 67. East Cumberland Bay, 3 cables north-east of Hobart Rock to \ cable west of Hope Point, South 



Georgia, 28 Feb. 1926, 38 m. 

 St. WS 25. Undine Harbour (North), South Georgia, 17 Dec. 1926, 18-27 m - 



Major diameter 14-2 mm.; minimum diameter 11-5 mm.; height 11-7 mm. (St. MS 67). 

 Major diameter 17-5 mm. ; minimum diameter 14-5 mm. ; height 14-0 mm. (St. MS 10). 



Margarella (Promargarita) tropidophoroides obsoleta n.subsp., PI. V, fig. 4 



This is a form of tropidophoroides with the spiral keels reduced to a weak biangulation. 



Shell thin, depressed-turbinate, very weakly biangulate, imperforate, pale yellowish brown with 

 a white zone surrounding the umbilical area and occasionally a narrow white band at the lower sub- 

 angle. Spire half height of aperture. Uniformly sculptured with numerous deeply incised spiral lines. 

 Whorls five, broadly rounded, but weakly angulate above the middle on the spire-whorls, and at the 

 periphery. The spirals number seven on the first post-nuclear whorl, fifteen to twenty on the penulti- 

 mate and about forty-five on the body-whorl. The columellar callus is white, broad, concave and 

 completely fills the umbilical area. Compared with achilles of similar size, obsoleta has a taller spire, 

 a more rounded aperture, is of lighter colour and has evenly developed spirals over the whole shell. 



Major diameter 13-5 mm.; minimum diameter n-o mm.; height n-o mm. (St. MS 6). 



Type locality. St. MS 6. East Cumberland Bay, \ mile south of Hope Point to 1^ cables SxE 

 of King Edward Point Lt., South Georgia, 12 Feb. 1925, 24-30 m. 



Margarella (Promargarita) achilles (Strebel) 



Photinula achilles Strebel, 1908, p. 73, pi. 5, fig. 69a, b. 

 Type locality. South Georgia, 1-2 m. 

 St. 145. Stromness Harbour, South Georgia, between Grass I. and Tonsberg Point, 7 Jan. 1927, 26-35 m - 

 St. MS 6. East Cumberland Bay, \ mile south of Hope Point to i\ cables S x E of King Edward Point Lt., 



South Georgia, 12 Feb. 1925, 24-30 m. 

 St. WS 25. Undine Harbour (north), South Georgia, 17 Dec. 1926, 18-27 m - 



This is a large, thin-shelled species, depressed-turbinate, with a relatively large ovate aperture. It is 

 light reddish brown with a broad zone of white surrounding the umbilical area, occasionally a narrow 

 white band just below the periphery and rarely a second narrow white band above the periphery. The 

 body-whorl is weakly biangulate. Sculpture consisting of incised lines, clearly shown on the early 

 whorls and around the umbilical area, but obsolete elsewhere. In the adult there are about eight 

 lirations on the early whorls and six or seven around the umbilical area. The umbilicus is completely 

 covered by a broad concave white columellar callus. Strebel compares this species with expansa, but 

 the relationship is certainly with Promargarita tropidophoroides. 



Major diameter 19-0 mm. ; minimum diameter 16-2 mm. ; height 16-5 mm. (St. WS 25). 



Dentition. The radula is scarcely distinguishable from that of tropidophoroides. 



