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a dense tuft of pectinated spines (Pl. XXVII, fig. 22) which Darwin sometimes observed 
in this species also and which according to him occur in specimens from La Plata. The outer 
surface of the pedicel of this cirrus bears the tuft of long spines as described by Darwin. 
The cirrus of the third pair has rami of nearly equal length, both composed of 14 
segments. The number of pairs of spines on the inner side of the segments is four, the length 
of the spines greatly diminishing from the upper to the lower pair. The third pair of cirri have 
exactly the same structure as the fourth, the latter, however, are slightly longer and have 
16 segments in each ramus in the specimen which was examined. The sixth pair has 18 seg- 
ments in both rami. 
The penis is very long, more than twice as long as the cirri of the last pair. It is 
distinctly ringed, broad at the basis and much narrower towards the extremity. A few delicate 
hairs are scattered over its surface, the last segment bearing a tuft of such hairs disposed on 
both sides of a somewhat elongate slit-like opening. 
To this species, most probably, belong also a few small specimens of a Chthamalus 
attached to a piece of rock or stone, found on the reef at Sapek-Bay, East-coast of Sumbawa. 
They are very small specimens and they are slightly different from each other. The largest has 
a diameter at the basis of about 5 mm., the smaller ones of 2.5 and 3 mm. respectively. Whilst 
the smaller ones have the orifice of an elongate shape, that of the larger specimen is about 
as long as broad. Of the latter specimen the opercular valves were examined. Its scutum 
is triangular, with the basal and opercular margins long, the tergal margin relatively short. It 
is feebly folded in the direction from the apex to the middle of the basal margin, the latter 
being distinctly hollowed out about the middle. The tergum is small; it has a very prominent 
articular ridge, the part corresponding with the spur of other species rather broad and rounded 
at the extremity; it has the opercular margin short and distinctly arched, and it is furnished 
with very prominent crests for the adductor muscle, the extremities of which reach distinctly 
beyond the basal margin. The colour of the smaller specimens is dirty olive-greenish, that of 
the larger one blackish-blue. The basis of the larger specimen is on one side, and partly over- 
grown by the shell of a Lamellibranchiate Mollusc — a circumstance that does not make 
it easier to give a good description. The alae of the rostrum are well-developed, broad at 
the upper extremity and terminating downwards into a point; the radii of the rostro-lateral 
compartments are indistinct, but certainly very narrow. The little stone with these small 
Barnacles was collected on the reef along the coast of Sumbawa during shore-exploration, 
and was found, probably, at a very inconsiderable depth. 
2. Chthamalus intertextus Darwin. 
DARWIN, CH., Monograph. The Balanidae, Verrucidae etc. 1854. p. 467, pl. XIX, fig. ta, 14. 
At Station 16 a single specimen was collected, in very defective condition, and | 
think that it belongs to this species. The oblique interfolding laminae of the parietes, the 
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