BARNACLES OF JAPAN AND BERING SEA. 
79 
seen to be marked with rather regularly spaced transverse darker lines, those near the base bearing 
fine shining bristles in a single close series. These bristles are largely lost on the older part of the wall, 
and some specimens lack them entirely. 
The rostrum is the largest plate, triangular in shape. Its sheath is tripartite, as usual. The 
rostral latera are nearly as large. Like the carinal latera and carina, it has a well-developed, distinctly 
sunken ala. The carinal latera are very narrow. The carina is V-shaped in upper view. 
The sheath occupies more than half the total height. It is closely ridged transversely, the ridges 
narrow, not hairy. Its lower edge is continuous with the surface below it, not in the least overhanging. 
The base has a calcareous rim at the edge, sometimes as much as 6 mm. wide. The central part 
is membranous. 
Altitude of cup about 32 mm. greatest diameter of base 30 mm.; of orifice 16 mm. 
The scutum (pi. xv, fig. 5, 6, 7) is curved, the outer side concave, covered with a dense golden 
olive cuticle. It is sculptured with well-raised transverse thread-like ridges, each bearing a close 
row of minute shining spicules. Along the occludent edge there is a series of oblique nodes, formed by 
the enlarged extension of every alternate ridge of the outer surface (pi. xv, fig. 5). Internally there 
is a somewhat massive but low articular ridge extending along two-thirds of the scutal margin. The 
articular furrow is deep but very narrow. The adductor ridge is represented by a low callus only. 
The pit for the depressor muscle has several short but emphatic crests. 
The tergum is covered with yellowish cuticle paler than that of the scutum. It has a concave 
scutal border, the adductor ridge not projecting beyond it. The convex carinal margin is equal in 
length to the basal margin. The spur is short, rather wide, and separated by about half its width 
from the baso-scutal angle. A slight depression, marked only with arcuate growth-lines, runs to the 
spur. On the scutal side of this band the surface has narrow arched thread-like riblets. The larger 
area on the carinal side of the spur-band has similar oblique riblets. There are no noticeable longi- 
tudinal striae. The articular ridge is arcuate, rather high; the articular furrow broad and shallow. 
