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a dense tuft of pectinated spines (PI. 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. lts 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 inconsiclerable depth. 



2. Chthamalus intertexttis Darwin. 



Darwin, Ch., Monograph. The Balanidae, Verrucidae etc. 1854. p. 467, pi. XIX, fig. ia, ié>. 



At Station 16 a single specimen was collected, in very defective condition, and I 

 think that it belongs to this species. The oblique interfolding laminae of the parietes, the 



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