SYSTEMATIC 145 



The species is nearest allied to Probuccinum tenuistriatum Hedley (1916, p. 58, pi. 8, figs. 95, 96). 

 Compared with the South Georgian species, tenuistriatum is proportionately wider and has the addition 

 of a varix near the outer lip. 



Probuccinum angulatum n.sp., PI. VII, fig. 27 



Shell broadly conical with a sharply angled periphery on the last whorl ; smooth, except for weak 

 irregular axial growth folds ; white, covered with a thin, pale buff epidermis. Protoconch conical, erect, 

 of 2§ smooth whorls with a bluntly rounded tip. The holotype has two post-nuclear whorls but is 

 evidently not adult. Operculum horny ovate-pyriform, slightly produced on the lower inner edge and 

 with a terminal nucleus. 



Type locality. St. 156. North of South Georgia, 53 51' S, 36 21' 30" W, 20 Jan. 1927,200-236 m. 

 St. 159. North of South Georgia, 53 52' 30" S, 36 08' W, 21 Jan. 1927, 160 m. 



Height 9-9 mm. ; diameter 7-0 mm. (holotype). 



Dentition. Fig. K, 65, p. 193. St. 159. Unfortunately, the only example containing the animal has 

 an abnormal radula with five cusps on the left lateral and four on the right. The central is of similar 

 shape to that of delicatulum, but it also is abnormal in having an additional weak cusp between the 

 central cusp and the right-hand outer one. 



This species is of heavier build than delicatulum, and although the material is not adult the species 

 will be easily recognized by its strong peripheral angulation. 



Genus Cavineptunea n.gen. 

 Type: Cavineptunea monstrosa n.sp. 



This genus is provided for a Neptunea-like shell with a remarkable protoconch, quite unlike any 

 other I have seen. It is large, like a tall, spirally wound collar, and surrounds a deep apical cavity. The 

 nucleus is small and central, and the spiral collar emerges from it with rapidly increasing whorls. The 

 effect is definitely neither the result of erosion nor the loss of a prior horny envelope. A juvenile in 

 a perfectly non-eroded state has a protoconch of exactly the same form. The operculum is irregularly 

 ovate with a blunt terminal nucleus, and the radula consists of a tricuspid central tooth and three or 

 four cusps on the laterals. A similar abnormality is shown in Troschel & Thiele's figure of the radula 

 of N. bulbacea (1868, pi. 6, fig. 16) which has three cusps on one lateral and four on the other. Un- 

 fortunately, I was able to prepare only one radula mount, so the normal number of lateral cusps is in 

 doubt. 



The shell is tall-spired, with a short, twisted canal and an angulate periphery. 



It is difficult to determine whether Cavineptunea is an Antarctic relative of the Neptuniidae or simply 

 another example of the adaptive radiation so marked in the Cominellid-Buccinuloid assemblage of the 

 southern regions, but the latter supposition is the more likely. Unfortunately, the only available animal 

 was not well enough preserved to do more than examine the dentition. 



Cavineptunea monstrosa n.sp., PI. VIII, figs. 38, 39 



Shell thin, white, with a film of yellowish buff epidermis. Spire tall, if times height of aperture; 

 base concave, strongly contracted; pillar flexuous. Whorls seven, including a relatively large concave 

 protoconch of about z\ whorls, with a tall, straight-sided spiral rim, as described above. The first whorl 

 of the protoconch is smooth, but the second develops closely spaced, weak, flattened spiral cords, and 

 the carinate edge rapidly resolves into one of these spirals as the coiling becomes normal with steep 

 straight-sided whorls. First post-nuclear whorl with ten flattened linear spaced spiral cords, penulti- 

 mate with sixteen, and body whorl, including base, with thirty-eight. Aperture obliquely pyriform; 



13-2 



