194 
Records of the Australian Museum (2017) Vol. 69 
Distribution. The writer is not aware of fossils of Janthina 
exigua. Janthina exigua is probably the most widely recorded 
of all living Janthina species. However, its distribution 
provides some surprises. It is the most common Janthina 
species in most beach strandings around New Zealand and 
southern Australia, whereas it is one of the least common 
species in the North Pacific, although it is among species 
recorded from Japan (as far north as Boso Peninsula, Honshu; 
Higo et al. 1999: 173). There seem to be few records from 
northern Australia, including Queensland. Savilov (1969: 
398—403) described the distribution of Janthina species at 
393 stations where Janthina was sampled by RV Vityaz in 
the Pacific. J. exigua was collected at only four of these 393 
stations, all near the North Island of New Zealand. However, 
Savilov also noted that Laursen (1953) recorded J. exigua 
from further north in the South Pacific, to 10°S, from New 
Caledonia east to Tahiti, in the southern Indian Ocean, and 
near Hawaii, and that Fowler (1948, 1949) and Wilson & 
Wilson (1956) recorded J. exigua from the southern coasts of 
Britain. In contrast to all these observations, Benson (1860: 
406) noted that exigua was the most widely distributed 
species met with” during a voyage from England to Calcutta 
in the Malcolm , correctly pointing out that I. capreolata 
Montrouzier is not separable. He first observed specimens 
two days before reaching Madeira (Benson, 1860: 405), and 
then observed specimens almost throughout the voyage. 
Benson’s careful distinctions between subtle forms, his 
comments on the synonymy of Reeve’s and other species 
names, and his references to publications by Coates (1825), 
Reeve (1858) and Morch (1860) show that his observations 
are very reliable. Janthina exigua occurs throughout the 
world tropical and temperate ocean, as far south as Orange 
Bay, Tierra del Fuego (type locality of J. courcellei) and 
Mason Bay, Stewart Island, southern New Zealand (listed 
above), but most reporters have described it as less common 
than other species in the northern Pacific and Indian Oceans. 
Dimensions. See Table 8. 
Diagnosis. Small, few specimens over 20 mm high; spire 
tallest of all Janthina species, but height variable; whorls 
evenly and strongly convex, suture deeply impressed; 
sculpture of prominent, thin, closely spaced, commarginal 
axial ridgelets over entire teleoconch, c. 0.2-0.5 mm apart 
at periphery of large specimens, angulated in conformity 
with sinus. Sinus occupying entire height of outer lip, deep, 
sharply V-shaped, apex in centre of lip. Most specimens deep, 
intense violet, some paler, very few with pinkish tinge. Lays 
ovate-triangular egg capsules on underside of float. 
Table 8. Dimensions of Janthina exigua. 
locality 
height 
diam. 
H/D 
GNS RM5311, Piha Beach, W Auckland, NZ 
19.5 
16.7 
1.17 
GNS RM5311, Piha Beach 
18.3 
16.1 
1.14 
GNS RM5311, Piha Beach 
16.7 
15.7 
1.06 
GNS RM5626, Nukumaru Beach, Whanganui, NZ 
16.9 
14.9 
1.13 
GNS RM5626, Nukumaru Beach 
16.0 
13.6 
1.18 
GNS RM5626, Nukumaru Beach 
15.9 
13.9 
1.14 
GNS RM5626, Nukumaru Beach 
16.2 
14.3 
1.13 
GNS RM5626, Nukumaru Beach 
17.2 
14.1 
1.22 
NMNZ M277699, Karioitahi Beach, Waiuku, NZ 
20.7 
17.6 
1.18 
NMNZ M277699, Karioitahi Beach 
20.8 
18.8 
1.11 
NMNZ M277699, Karioitahi Beach 
20.3 
17.8 
1.14 
NMNZ M277699, Karioitahi Beach 
19.7 
18.3 
1.08 
NMNZ M277699, Karioitahi Beach 
22.0 
17.2 
1.28 
NMNZ M214377, Raoul I, Kermadec Is. 
18.1 
15.1 
1.20 
Remarks. The small, deep violet species Janthina exigua is 
the most coarsely sculptured of living Janthina species, the 
only one with obvious, coarse axial ridges up to c. 0.5 mm 
apart over the entire exterior of large shells, resembling the 
axial sculpture of J. typica, J. chavani and J. krejcii sp. nov. 
and of a finely sculptured Epitonium species. Measurement 
of the spacing of the axial ridges on SEM images (Fig. 34B) 
showed that on this small specimen of J. exigua the ridges 
are c. 120-200 pm apart at the periphery, whereas on the 
specimen of J. umbilicata examined by SEM (Fig. 34D) the 
ridges are only c. 30^10 pm apart at the periphery. The axial 
lamellae of J. exigua also are considerably higher and more 
prominent than those of J. umbilicata. The apex of the outer 
lip sinus is at the periphery, i.e., in the centre of teleoconch 
whorls, and leaves a clear trace of the sinus apex around the 
centre of all whorls of tall-spired specimens. The consistently 
deep coloration is also a species character, the colour varying 
from deep reddish violet to (much more commonly) deep 
bluish violet, with a narrow paler zone beneath the suture in 
a few specimens. The radular teeth (Laursen, 1953: fig. 24) 
are similar to those of J. umbilicata , but have shorter bases, 
and some are less strongly hooked than those of J. umbilicata. 
The float (e.g., Laursen, 1953: fig. 1; Bennett, 1966: pi. 9, 
fig. 2) is proportionally the longest and narrowest of all 
Janthina species, although a specimen photographed alive in 
northern New South Wales by Denis Riek (Brunswick Heads, 
NSW; Fig. 5C) demonstrates that the float of J. umbilicata is 
indistinguishable from that of J. exigua. The distinctiveness 
of J. exigua is attested by the remarkably few synonyms it 
has received in this vastly over-named genus. 
Time range. No fossil record; living only. 
Janthina pallida Thompson, 1840 
Figs 2K-L, 5B 
Janthina pallida Thompson, 1840: 96, pi. 2, fig. 2 (under 
“J. nitensT, name attributed to Harvey; tentatively a 
new species). 
Janthina pallida Harvey.-Thorpe, 1844: 152;Kuster, 1868: 
5, pi. 1, fig. 5; Monterosato, 1878: 95; Locard, 1898: 2; 
Dali, 1908: 318. 
Ianthina striolata A. Adams & Reeve, 1850: 54, pi. 11, fig. 9; 
H. Adams & A. Adams, 1854: 87; Reeve, 1858: pi. 5, figs 
24a-b; Hedley, 1900:141; Pritchard &Gatliff, 1900: 141; 
Macpherson& Chappie, 1951: 124; Cotton, 1959: 376. 
Ianthina pallida Harvey.-Forbes & Hanley, 1853: 553, pi. 
69, figs 10-11; H. Adams & A. Adams, 1854: 87; Reeve, 
1858: pi. 4, figs 20a-b; Benson, 1860:412; G. B. Sowerby 
II, 1882: 51, pi. 444, figs 19-20. 
Janthina (Amethistina) pallida Harway [sic].-Morch, 1860: 
281. 
Janthina (Amethistina) striolata Adams & Reeve.-Morch, 
1860: 282. 
Amethistina pallida { Harvey).-Monterosato, 1884: 105. 
Janthina pallida (Harvey Mss) Thompson.-Bucquoy et al ., 
1886: 435, text-fig. 7. 
Ianthina globosa var. pallida Harvey.-Tryon, 1887: 37, pi. 
10, figs 15-16. 
Janthina (Amethistina)pallida Harvey-Thiele, 1929, p. 225; 
Priolo, 1959: 186. 
Ianthina pallida Thompson.-Laursen, 1953: 31, figs 36-39; 
Macpherson & Gabriel, 1962: 119. 
Ianthina globosa Swainson.-Morton, 1954: 167 (in part J. 
pallida, misidentified as J. globosa). 
