270 SCALPELLUM PERONII, 



has no other character which at all justifies its generic 

 separation. In the shape of the scuta and carina it 

 comes nearest to 8. vulgare. Taking all the characters 

 together, it is scarcely possible to say to which of the 

 other species it is most closely allied, having close affini- 

 ties with all. In the entire structure, however, of the 

 Complemental Male, immediately to be described, this 

 species certainly comes nearer to S. villosiim than to any 

 other species. I may add, that in S. vittosum the latera 

 are almost rudimentary, and therefore tend to disappear, 

 whereas in S. Peronii it is the calcareous scales on the 

 peduncle which have actually disappeared. 



COMPLEMENTAL MALE. PL VI, fig. 3. 



I examined, owing to the great kindness of Mr. Cuming, 

 six dry specimens of the hermaphrodite S. Peronii, from 

 Swan River, and one in spirits from another locality, in 

 the British Museum. Out of these seven specimens, only 

 three appeared to have had parasites attached to them, and 

 these I infer, from reasons to be more fully given at the 

 end of the genus, are Complemental Males. One of the 

 three specimens, however, had two males close together. 

 These parasites were firmly cemented to the integument of 

 the hermaphrodite, in a fold, in a central line between the 

 scuta, a little below (the animal being in the position in 

 which it is figured) the adductor scutorum muscle, and 

 therefore some way below the umbones of these valves. 

 When the scuta are closed, the parasites, from their small 

 size, are enclosed and protected. In every detail of struc- 

 ture, they are obviously pedunculated Cirripedia. 



The Capitulum (PI. VI, fig. 3) has six valves ; namely, a 

 pair of scuta and of terga, a carina, and a rostrum, all united 

 by finely-villose membrane, furnished near the orifice with 

 some much longer and thicker spines. The capitulum is 

 truncated in a remarkable manner, the orifice not being, 

 as in the hermaphrodite, in the same line with the 

 peduncle, but almost transverse to it, and therefore almost 



