COMPLEMENTAL MALE. 279 



a scutum being here ^ths of an inch in length. The 

 carina descends only just below the basal points of the 

 terga, instead of far below them. The rostrum is a little 

 broader and more arched than the carina ; it is y—ths in 

 length, and therefore more than two thirds of the length 

 of the carina, the latter being -fifths of an inch from the 

 apex to the basal margin. The primordial valves, with 

 , the usual hexagonal tissue, are seated on the tips of the 

 scuta, terga, and carina, but not on the rostrum ; so that 

 these valves follow the same law of development, as in the 

 ordinary and hermaphrodite form of Scalpellum. The 

 scuta {a, fig. 4, greatly enlarged), the terga {b), and carina 

 (c) of the male, resemble the same valves in the herma- 

 phrodite, much more closely than do these valves in the 

 male and hermaphrodite S. Peronii. The rostrum has not 

 its basal margin hollowed out, and is very much larger 

 relatively to the carina, than in the hermaphrodite. The 

 large relative size of the rostrum in the complemental male 

 both of this species and of S. Peronii, is a remarkable 

 character, which I can in no way account for. 



The peduncle is narrow and short, but in a different 

 degree in the two specimens examined. It is naked. The 

 prehensile antennae were not in a good state of preserva- 

 tion : the disc is narrower than the basal segment, and 

 only slightly pointed, in which important respect it differs 

 from the same part in the foregoing species ; at its distal 

 end, rather on the inner side, there are two or three 

 spines, apparently in place of the excessively minute hairs, 

 which are found at the same spot in some or in all the 

 other species of Scalpellum, and in Ibla : similar strong- 

 spines occur in Pollicipes. Unfortunately, for the sake of 

 comparison, I was not able to find the prehensile antennae 

 in the hermaphrodite S. vittosum. 



Mouth. — Labrum bullate, with teeth on the crest. 

 Palpi blunt, spinose. 



Mandibles, with three teeth ; inferior point rather 

 strongly pectinated. 



Maxillce, with a considerable notch under the upper pair 

 of large spines ; inferior part of the edge not prominent. 



