28S BALANID^E. 



shorter ramus of the first pair, and has ten or twelve segments. The 

 third pair is above twice as long as the second pair, and contains 

 twenty-four segments : this very unusual length is owing to the pre- 

 sence of numerous thin tapering upper segments, unlike those gene- 

 rally found in Balanus, in the third pair of cirri, and apparently serving 

 as feelers. These upper tapering segments «ire of an inverted conical 

 shape, and support on their upper margins two very small tufts of 

 spines, one behind and one in front : on the segments lower down these 

 tufts increase in size, and the spines are more spread out, so that in 

 the basal segments, the tufts in front form on the upper margin two 

 or three crowded rows of bristles. The three posterior pairs of cirri have 

 elongated segments, which bear on their upper half three pairs of 

 spines ; of these the lowest pair is minute, and the middle pair is only 

 one third of the length of the upper pair. The sixth cirrus, in the 

 same individual as before, contained twenty-seven segments in each 

 ramus, that is only three more than in the third cirrus! I must 

 observe, that the cirri in all the specimens were irregular, often dis- 

 torted and monstrous ; and therefore, probably, there is considerable 

 variation in the proportional numbers of the segments in the cirri. 



At the base of the penis there is a minute, knife-edged, triangular 

 projection. The branchiae are rather narrow, pointed, and not very 

 large. 



Affinities. — This is a very distinct species, as shown by the peculiari- 

 ties in the cirri, by the absence of radii to the shell, and by the pre- 

 sence of crests for the attachment of the lateral scutal depressores. 

 With the exception of this latter character, the opercular valves clearly 

 show, that B. vestitus is allied to B. allium, cepa, and quadnvittatus. 

 In some respects this species manifests an affinity to B. imjperator, 

 which latter has its third pair of cirri nearly similar to those of B. 

 vestitus. 



39. Balanus imperator. PI. 8, fig. 4 a — 4 c. 



Shell internally imperial purple ; parietes thick, with their 



internal basal edges rough ivith irregular points and ridges ; 



radii narrow; basis very thin, solid. Scut inn, with crests 



for the rostral and lateral depressor muscles : tergum, with 



the end of spur rounded. 



Eab. — New South Wales, Sydney, Port Stephens, Moreton Bay ; attached to 

 sandstone-rocks and shells, at low-water line ; Mus. Brit., College of Surgeons, 

 Cuming, Stutchbury. 



Shell conical, very thick and very strong ; longitudinally sulcated 

 more or less strongly; whole thickness of shell beautifully coloured 

 rich violet, or more strictly "imperial purple"; externally the surface, 

 from disintegration, is generally whitish ; internally the colour is best 

 developed : the narrow radii and the thin basis are white. The largest 



