A. Wakefield 
A review of Marginella bicatenata 
Type species: Voluta glabella Linnaeus, 1758, by 
monotypy. 
Marginella bicatenata G.B. Sowerby (III), 1914 
Figs 1-21 
Marginella bicatenata Sowerby (III), 1914: 147, pl. 
19, fig. 7. 
Marginella tomlini Shackleford, 1916: 193, text figs 3, 
4. 
Type material. Marginella bicatenata ,1 ad sh., 
holotype, preserved dry, 13 x 7 mm, Gorée, col 1. 
Tomlin (ex. Coll Denans), NMW.1955.158.01434, 
(Figs 1,2). 
Marginella tomlini , 1 ad. sh., holotype, preserved dry, 
18 x 10 mm, off Cape St. Blaize in 105 fms, SAM 
A3704 (Figs 13-15). 
Other material examined. 6 ad and 1 juv. sh, from 
KwaZulu-Natal, preserved dry: 12.8 x 6.9 mm, 
29.825° S 31.2383°E, NM ref. no. D3819 (Figs 3,4); 
13.9 x 7.5 mm, 30.0132° S, 31.06°E, NM ref. no. 
DI 159 (Figs 5,6); 15.7 x 8.5 mm, 30.0067° S 31.05°E, 
NM ref no. DI 094 (Figs 7,8); 13.5x6.6 mm, juv., NM 
ref. no. E8656 (Figs 9, 10); 11.7 x 6.8 mm, 30.0182° S 
31.0533°E, NM ref. no. D800 (Figs 11, 12); 14.6 x 8.8 
& 12.8 x 7.4 mm, 30.1067° S 31.0133°E, NM ref. no. 
D1946. 
2 ad sh., from the Southern Cape région, preserved 
dry: 17.8 x 9.95 mm, Agulhas Bank, dredged, depth 
unrecorded, AWC; 16.2 x 9.33 mm, Southern Agulhas 
Bankat 100m, AWC (Figs 16, 17). 
Type Locality. Gorée, Sénégal (in error) 
Descriptive notes. Shell thin, smooth, length 11.5-18 
mm, W:L ratio 54-60% (mean 56%), strongly biconic 
to elongated biconic. Spire elevated, of 4.5 whorls 
including paucispiral protoconch, stepped (mainly 
between penultimatc and last adult whorl) to straight 
sided. Shoulder smoothly rounded to slightly 
angulated, shell tapering to narrow, slightly truncated 
anterior end. Creamy white, pale straw to pale grey 
body whorl, with two spiral rows of blurred charcoal 
grey spots: anterior row of 6-8 spots emerges from 
aperture immediately posterior to 4 th plication, ending 
at anterior l/6 th of lip; posterior row of 7-10 (on body 
whorl) spots at shoulder level. Posterior row continues 
onto spire to reach plain, glassy protoconch. Suture 
not impressed. Lip, plications, base of columella 
white. Aperture approximately 1.5 x as wide as labial 
varix. Lip smooth, straight to gently convex, thickened 
externally as a single moderately strong varix with a 
smooth rolled edge. Varix groove présent externally. 
Siphonal notch absent, posterior notch weak, lip thins 
slightly in posterior l/6 th before inserting to body 
whorl at shoulder at level of posterior row of spots, or 
just anterior to it. Lip continues round anterior end, 
thinning out completely to join base of columella at 
end of First plication. Columella with 4 moderately 
strong, thin, single plications, gradually increasing in 
séparation from l sl to 4 lh . First two oblique, 3 and 4 
becoming more horizontal. Plications fill ovei /i but 
less than 2/3 of aperture. Columella slightly concave 
in région of plications. Pariétal surface smooth, 
weakly convex to straight. Anterior and posterior 
callus absent. Animal unknown. 
Distribution. Off central KwaZulu-Natal to Cape St. 
Blaize, southem Cape, South Africa, depth range 100- 
200 métrés. 
Remarks. The species is listed by Tomlin (1917: 253) 
who records the holotype of M. bicatenata as being 
présent in the Tomlin collection. The Melvill-Tomlin 
Collection was received by Amgueddfu Cymru 
(NMW) in 1955, and enquiries hâve confirmed that 
the holotype is présent in the collection. It is biconic in 
profile (Figs 1, 2) and from the ventral view has three 
large spots at the shoulder and four at mid-body. It 
clearly is the shell depicted and described by Sowerby. 
Similarly robust, relatively small, dirty-white shells 
with charcoal coloured spots and with a variety of 
strong morphologie features such as stepped spires, 
and strongly angulated shoulders are lound at the 
north-eastern end of the range, off KwaZulu-Natal 
(see the specimens from the NM in Figs 3-12). As the 
holotype exhibits these characters it is much more 
likely to hâve originated from Natal than from the 
Southern Cape, and the original type locality has 
always been erroneous - this is emphatically not a 
West African shell. 
Millard (1981, fig. Da, p. 6, 7) figured a specimen 
présent in the SAM (ref. A3704), citing it as the type 
of M. bicatenata . As noted above, the holotype of M. 
bicatenata is in the NMW. The specimen to which 
Millard was referring is in fact the holotype of M. 
tomlini Shackleford, 1916 (Figs 13-15). The original 
description of it featured a quality photograph of the 
holotype - one of the earliest original descriptions to 
do so - and its identification as the holotype of M. 
tomlini is beyond any doubt. Shackleford recorded the 
type locality as off Cape St. Blaize, southem Cape, 
South Africa, C N. by E. Vi E., distant 68 miles - 105 
fathoms {sic) 9 . M. tomlini is considered to be a junior 
synonym of M. bicatenata , and represents the form 
found at the Southern end of the range. These shells 
are larger and thinner walled than their northem 
counterparts, and they also inhabit relatively shallower 
waters in the south. This trend is observed in most 
other species of South African marginellidae with a 
similar distribution pattern. This progressive 
morphological change has been attributed to many 
factors, one being the availability of food (the cooler 
waters ot the Cape are rich in nutrients compared to 
the warmer waters of KwaZulu-Natal). 
One ot the NM specimens (Figs 9, 10) of M. 
bicatenata is in exceptional condition and is very well 
marked, and even shows extra fine spiral lines of spots 
70 
