112 W.B. Rudman 
Figure 1. Pelagic egg capsules of Nodilittorina unifasciata laid by snails collected at Harbord, Sydney, October 
1995. Capsule diameter 240 um. Photo: G.Avern. 
region of the concave face. The convex face of the capsule is perhaps best described as a dome, with a 
somewhat roughened surface, surrounded by a wide cylindrical skirt. There is a distinct median ridge 
around the broad outer edge of the skirt. 
Because of the extreme transparency of the capsule, external sculpture is only visible by 
manipulating the direction of incident light falling on the capsule. There is clearly a median ridge on 
the outer half (‘skirt’) of the capsule. In some angles of light, under the microscope, it is possible to 
consider that there is a ‘thickening’, or rounded ridge, at both the outer and inner edges of the capsule 
skirt. The widest diameter of the capsule is 240 um, and the egg diameter approximately 100 um. 
Discussion 
Rosewater (1970) suggested that the Australian М. unifasciata and a common, similarly coloured 
New Zealand species, М. antipoda (Philippi) (= Melaraphe oliveri Finlay), were subspecies. The 
latter species is found throughout New Zealand, has a characteristic blue and white shell, and is 
seldom greater than 1cm in height. A comparison of the reported morphology of the planktonic egg- 
capsules of N. antipoda, and a second New Zealand species, Nodilittorina cincta (Pilkington, 1971), 
with the egg-capsules of N. unifasciata from Australia, suggests that either the two ‘subspecies’ аге 
distinct species or that Pilkington (1971) misidentified the capsules she described. 
.The egg capsule of N. cincta, as described by Pilkington (1971)(Fig. 2A), is quite similar to that of 
М. unifasciata, while the egg capsule of М. antipoda (as M. oliveri) (the supposed subspecies of N. 
unifasciata), is quite different (Fig. 2B). Іп М. cincta, the egg capsule has a broad outer skirt with а 
distinct ridge, surrounding a central dome-shaped region, similar (о М. unifasciata. Both are very 
similar in diameter. In comparison, the egg capsule of М. antipoda is much more regularly dome- 
shaped. Veliger larvae hatch from the capsules of both N. cincta and N. antipoda 3-4 days after laying 
(Pilkington, 1971), while I have observed hatching in N. unifasciata within 18 hours. 
