Beu: Evolution of Janthina and Recluzia 
197 
Other material examined. Present-day samples from Australia and New 
Zealand: Australia: Tasmania : (NMNZ M202862). New South Wales : 
Bermagui (AMS C40691, C40693); Port Stephens (NMV; AMS C91949); 
Putty Beach, Kilcare (AMS); Long Reef, Collaroy (AMS); Manly Beach, 
Sydney (AMS C32373, C56810); Cronulla (NMV); Botany Bay (AMS 
C83048). Queensland : Green I. (AMS C9856); Rocky Isle (AMS); 
Caloundra (AMS); Point Lookout, Stradbroke I. (AMS). 
Kermadec Islands: Raoul I., Kermadec Is (NMNZ M00991, M202862, 
many). 
New Zealand: 13 km N of Great King I., Three Kings Islands (NMNZ 
M146405, 1); Cape Maria van Diemen (M277743, 1); South Cavalli 
Seamount (M281315, 1); Ocean Beach, Whangarei Heads (Ml 50840, 6); 
Waipu Cove, Northland (GNS RM4781, 2); Uretiti Beach, Bream Bay 
(M277742,1); Piha Beach, W Auckland (GNS RM5312,8); SW ofWaiuku, 
W coast Awhitu Peninsula, W Auckland (NMNZ M277700, 2; M277702, 
4; M277704, many; M277706, 7; M277708,3); Karioitahi Beach, W coast 
Awhitu Peninsula (M277710,2); Papamoa Beach, Tauranga (M147404,3); 
Boulder Bay, Motuhora I., Bay of Plenty (M042552,1); Nukumaru Beach, 
W of Whanganui (GNS RM5627, 6). 
Distribution. The writer is not aware of fossils of Janthina 
umbilicata. The 18 lots observed from the New Zealand 
region are listed above. Janthina umbilicata has not been 
recorded from New Zealand previously, other than in the list 
by Spencer et al. (2009: 206). The few records the writer is 
aware of from Australia are also listed above. There seem to 
be no records from the Northern Territory, Western Australia, 
South Australia or Victoria, and J. umbilicata and J. pallida 
seem to be largely mutually exclusive around Australia. The 
two species Janthina exigua and J. umbilicata seem to have 
closely similar distributions, J. umbilicata consistently being 
the less common, at least in the southern part of their range. 
Around New Zealand, small numbers of specimens occur 
in most large strandings of J. exigua , from Raoul Island, 
Kermadec Islands (where J. umbilicata is common) and from 
the Three Kings Islands to as far south as Whanganui, but the 
writer has seen no specimens of J. umbilicata from further 
south. Spencer (1982) reported that “seven J. umbilicata 
were found on Waitangi, Chatham Is.”, but although this 
is quite feasible, the writer has not seen specimens from 
the Chatham Islands. Few specimens have been observed 
south of the northeastern North Island warm-water region, 
extending from North Cape to East Cape. Because relatively 
few earlier authors have distinguished it from J. exigua , the 
range of J. umbilicata is poorly known, but it seems likely 
to occur with J. exigua throughout the world tropical and 
temperate ocean, although not extending quite as far into 
the southern temperate zone as J. exigua does. In contrast 
Table 10. Dimensions of Janthina umbilicata. 
locality 
height 
diam. 
H/D 
GNS RM5627, Nukumaru Beach, Whanganui, NZ 
14.8 
13.4 
1.10 
GNS RM5627, Nukumaru Beach 
13.7 
11.8 
1.16 
GNS RM5627, Nukumaru Beach 
12.6 
11.4 
1.11 
GNS RM5627, Nukumaru Beach 
10.8 
9.5 
1.14 
NMNZ M277708, Karioitahi Beach, Waiuku, NZ 
20.5 
19.0 
1.08 
NMNZ M277708, Karioitahi Beach 
20.0 
18.9 
1.06 
NMNZ M277708, Karioitahi Beach 
20.0 
18.6 
1.08 
NMNZ M277704, Karioitahi Beach, Waiuku, NZ 
19.2 
17.2 
1.12 
NMNZ M277704, Karioitahi Beach 
16.7 
14.7 
1.14 
NMNZ M277704, Karioitahi Beach 
16.5 
14.4 
1.15 
to its uncommonness around Australia and New Zealand, 
Savilov (1969: 398-399) reported that J. umbilicata was 
the most widespread and abundant Pacific Janthina species, 
collected at 333 of the 393 Vityaz stations where Janthina 
was collected. At many stations very large numbers were 
collected, up to 1000 specimens per 20 minutes of sampling. 
The largest specimens were 14 mm high. “Exceptionally 
large concentrations of mature individuals and young up to 
4-5 mm long were observed in the central regions of... the 
N and S subtropical circulation in the California Current 
belt and in the eastern regions of the trade wind currents. 
Their quantity, notably that of mature animals, decreased 
considerably in the trade wind countercurrent area” (Savilov, 
1969: 399). 
Dimensions. See Table 10. 
Diagnosis. Small, few specimens over 20 mm high; spire 
moderately tall, whorls evenly and strongly convex, suture 
deeply impressed; sinus occupying entire height of outer lip, 
deep, sharply V-shaped, with apex in centre of lip. Sculpture 
weak, of very fine, low, closely spaced, silky-looking, 
commarginal axial ridgelets over entire teleoconch surface, 
angulated in conformity with sinus; c. 30—40 pm apart at 
periphery. Most specimens deep, intense violet; a few paler, 
particularly large ones. Closely resembling J. exigua in all 
characters other than its much finer, lower axial sculpture and 
most specimens being slightly shorter. Lays ovate-triangular 
egg capsules on underside of float. 
Remarks. Janthina umbilicata closely resembles J. exigua , 
and the two have been confused in several Australian and 
New Zealand collections. Besides a slightly shorter spire in 
most specimens of J. umbilicata , the main difference is that 
the axial sculpture is much lower, finer and more closely 
spaced in J. umbilicata than in J. exigua , producing a finely 
striate, silky-looking surface. As noted under J. exigua , 
measurement of the spacing of the axial ridges on SEM 
images showed that on the specimen of J. umbilicata (Fig. 
34D) the ridges are only c. 30-40 pm apart at the periphery, 
whereas on the small specimen of J. exigua examined (Fig. 
34B) the ridges are c. 120-200 pm apart at the periphery. The 
colour also is rather consistently deep bluish violet; a few 
paler specimens occur, particularly the largest ones seen, but 
less commonly than in samples of J. exigua. Few specimens 
show more than a very slight umbilical chink, as the inner 
lip is expanded slightly to cover the umbilicus in most adult 
specimens of this as in all other Janthina species, and the 
epithet “umbilicata” is no more appropriate for this species 
than for any other. The radular teeth (Laursen, 1953: fig. 28) 
are similar to those of J. exigua , although slightly shorter, 
and are moderately long and strongly hooked for a Janthina 
species. Rather strangely, this species was not mentioned, 
even in synonymy lists, by Kiister (1868). Iredale (1910: 74) 
described,/, umbilicata as “It has the form of exigua , Lam., 
but, being destitute of the rough sculpture of that shell, has a 
shiny appearance... ”, and pointed out that d’ Orbigny (1841: 
414) distinguished this species carefully from J. exigua. 
Living specimens from northern New South Wales illustrated 
in colour on his web page by Riek (2017; Fig. 5C) have a 
long, narrow float identical to that of J. exigua. The attached 
egg capsules are pale pink, as in J. globosa. 
Time range. No fossil record; living only. 
