315 
Fig. 56. Balanus amphitrite f. hawaii- 
ensis from Honolulu. Inside view of 
the opercular plates. [X 5,s]. 
partment, and sometimes also a similar white area is present along 
the radii. Radii and alae are greyish or almost quite white. The 
sheath is dark brownish or violet with narrow whirish stripes. 
The compartments only exceptionally show a tendency to dev- 
elop ribs along the white lines; generally the surface is quite 
smooth. The pores of the parieties are large, at the base with small 
septae along the outer lamina; these 
septae disappear further upwards 
and do not bifurcate. The basis is 
almost quite smooth within. 
In its opercular plates the pres¬ 
ent form comes near to the forma 
inexpecta. The tergum is flat with 
a broad spur fasciole outlined by 
grooves; the spur is moreover very 
broad, it is rounded or more square. 
The articular furrow is broad and 
deep; the crests for the depressor muscles are small and hardly 
projecting below the margin. 
The scuta have only little prominent growth ridges and no 
longitudinal scratches whatever. The colour is here as in the terga 
a greyish white. The internal structure in every detail coincides 
with forma inexpecta ; also the deep oblong pit is present below 
the adductor ridge. The greatest difference is found in the shape 
of the plate: this is in the present form rather narrow; the tergal 
and basal margins are of all but equal length, and meet in an 
obtuse angle. 
In its anatomical features the present form exhibits so great 
peculiarities that we cannot deny the possibility that it really re¬ 
presents a species of its own. Especially the armature of the cirri 
is peculiar. Cirrus I and II are of the common type. In cirrus 
III, on the other hånd, the bullate segments of the rami on their 
anterior side carry several short and strong, beaklike spines, beside 
the long bristles which already tend to an arrangement in pairs 
along the anterior median line. On the posterior side the basal 
six segments of the rami carry one, the following segments two 
upwards curved, short and strong spines beside three or four hairs. 
In cirrus IV the transition to the shape of the posterior cirri 
