402 Dr. F. Mliller on Balanus armatus. 



tirely wanting. The maxillce have a straight margin, with 

 a very minute notch below the uppermost setae, or with- 

 out any such notch. There is no projection for the lower 

 bristles. The upper and the two lowest setse are only a little 

 longer than the longest of the middle ones. Only about one- 

 third of the upper margin of the maxillae is hairy. 



Cirri. — First pair : the longer branch is about twice as long 

 as the shorter one, sometimes still longer, and has twice as 

 many joints (eighteen to twenty) ; the last joints are consider- 

 ably longer than the lower ones, cylindrical, and beset at the 

 end with an almost complete circlet of set«. The shorter 

 branch has usually from nine to eleven short joints, with 

 densely setiferous processes on the bowed side, most consider- 

 able on the middle joints. 



Second pair short, stout, densely bristled ; the anterior or 

 outer branch with from eleven to thirteen joints, only about 

 one-fifth or one-fourth longer than the inner one ; the latter is 

 9-10-jointed, and about as long as the shorter branch of the 

 first pair. In cast skins, and also usually in other cases, the 

 longer branch is seen straightly extended, and the shorter one 

 slightly curved. 



Third pair : from the base of this pair of feet a line densely 

 beset with long thin hairs runs upwards towards the back. 

 In length and form this pair hold a middle place between the 

 short and stout cirri of the preceding and the long slender 

 cirri of the following pairs. The slightly longer anterior or 

 outer branch has about fifteen to seventeen joints, the hinder 

 branch one or two fewer. The branches are about as long as 

 the longer branch of the first pair. A larger or smaller num- 

 ber of the joints of both branches are armed on the curved 

 side with strong curved teeth : in young animals the armature 

 is weaker and confined to some of the middle joints ; in the 

 larger animals, only the last two joints of the outer and the 

 last four or five joints of the inner branch usually want the 

 teeth. The armature of the outer branch is always stronger 

 than that of the inner one. These hooked decurved teeth 

 (fig. 21) not only occupy the upper part of the strongly pro- 

 minent margin of the flexed side of the joints, but extend 

 thence, gradually becoming smaller, and finally converted 

 into mere minute points over a larger or smaller part of the 

 outer surface of the joints. This portion which is beset with 

 teeth and hooks is usually elevated, in the form of a low swel- 

 ling, a little above the sm-rounding parts. Besides the teeth of 

 the flexed side, there are, especially on the lower joints, acute 

 spinules directed upwards on the extended side, a few spines, 

 also directed upwards, on tlie outside of the upper margin, and 



