COMPLEMENTAL MALE. 263 



either be killed by the pressure of the scuta of the 

 Scalpellum, or they would destroy the latter, and in doing 

 so soon lose their own support, and thus necessarily perish! 



The one full-grown specimen of S. rostratum, in Mr. 

 Cuming's collection, was in a good state of preservation, 

 but dry. The three parasites were attached, as stated, 

 close under the labrum, between it and the adductor 

 muscle. They are constructed like ordinary Cirripedia, 

 and have a mouth, thorax and cirri, enclosed in a capitu- 

 lum, supported on a peduncle of moderate length and 

 narrow. The entire length of the capitulum and peduncle, 

 as far as could be ascertained in the shrivelled condition 

 of the specimens, was ^ths, and the greatest width of the 

 capitulum yj^ths of an inch. Both capitulum and pe- 

 duncle are hirsute with spines, nearly j^th of an inch in 

 length, mingled with shorter hairs in little rows of three 

 and four together. The figure (5) in PI. VI is merely 

 a restoration, as accurate as could be made from the 

 much shrivelled specimens. There are only three valves, 

 — namely, an oval carina (a), seated rather high up on the 

 capitulum, in a rudimentary condition and only T~th of 

 an inch in length, and a pair of scuta ; these latter consist 

 of a narrow, slightly curved plate, ^ths in length, 

 broadest at the lower end, where the breadth is T™ ths 

 of an inch. The prehensile antennas, at the end of the 

 peduncle, have pointed hoof-like discs : I was not able to 

 make out the other parts. It deserves notice, that in 

 the young specimen of the ordinary form of S. rostratum, 

 ^th of an inch in length, and therefore only thrice as 

 long as the parasites, all the valves were perfect, and 

 seemed to have followed the ordinary law of development. 



Mouth. — The largely bullate labrum is placed far from 

 the adductor, in the same manner as in the hermaphrodite. 

 The mandibles have three large sharp teeth, with the 

 inferior point very sharp and small, so that there is one 

 less tooth than in the hermaphrodite. The maxillae have 

 two or three large upper spines, the others being very 

 thin ; I believe the lower part is upraised and step-like, 



