$!2^ BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



BALANUS HAWAIENSIS, new species. 



Plate 48, figs. 1 to ig. 



Type.— C^i. No. 43474, U.S.N.M. 



Distribution. — Hawaiian Islands, 21 to 222 fathoms, on spines of 

 the sea-urchin Phyllacanthus tJiomasi Agassiz and Clark; collected 

 by the Albatross Hawaiian Expedition, 1902. 



A very small, strong, and firmly attached baniacle, with a solid, 

 calcareous basis and rather thick, solid (poreless) walls. Radii pink; 

 parietes white, or sometimes having some pink stains. 



The foim is oval, conical, with strongly ribbed parietes; carinal 

 latera have a single strong rib, the rostrum usually three, and the 

 other compartments tAvo ribs. The radii are rather wide and rather 

 deeply, regularly grooved transversely, their summits strongly 

 oblique. The aire have straight or arched and smooth summits when 

 unbroken, and are nearly level, so that the margin of the aperture 

 is nearly regular. The aperture is ovate, angular at the carinal end. 

 The sheath is very short and its lower border does not overhang. 

 Below it the inner surface of the parietes is smooth, becoming ribbed 

 near the base. Basal edges of the wall plates are thick and crenu- 

 lated. The articulating borders of the radii are finely crenulated, 

 as are the opposed sutural surfaces. The basis is thick. 



Length of base 3.2 mm., width 2.8 mm., height 1.5 mm. 



Length 5 mm., width 3.5 mm., height 2.2 mm., largest specimen. 



The white opercular plates lodge close to the aperture and project 

 above it The scuta are sculptured w^ith flat, regular growth-ridges, 

 about every second or third one forming a tooth on the occludent 

 margin. These teeth, interlocking in the closed barnacle, produce 

 a crenellated occludent suture. There is a rather prominent, acute, 

 somewhat reflected articular ridge, nearly the whole length of the 

 tergal margin, and a narrow articular groove. There is no trace of 

 an adductor ridge. The scar of the adductor muscle is small and 

 distinct. 



The terga are nearly twice as long as wide. Externally there are 

 very weak ridges of growth except on the band leading to the spur, 

 where the ridges are stronger and arcuate. This band is not de- 

 pressed, but is separated from the rest of the surface by a slight 

 radial depression. The spur is very short, tapering to a rounded 

 end. Its outline passes imperceptibly into that of the basal margin. 

 Inside there is a moderate articular ridge about one-third the length 

 of the plate. There are about five rather strong crests for the de- 

 pressor muscles. 



The labrum has three short, conical teeth on each side of the deep, 

 narrow median notch (fig. 70?^). 



Palpi armed with very long hairs (fig. 7lc). 



