204 BULLETIN 93^ UNITED STATES NATIONAL MUSEUM. 



h^. Scutum longitudinally striate; an angle near the lower end of the thin 

 articular ridge. Radii very wide; within the base the crests of the 

 parietal ribs are sharp or rounded, and their tapering lower ends are 



crenulate B. hameri. 



b\ Scutum not striate longitudinally ; its articular ridge very low and broad, 

 not angular. Radii rather narrow ; within the base the crests of the 

 parietal ribs are flattened, and their tapering lower ends are smooth 



B. cvcrmanni 

 o■^ Tropical group (Striatohalamis). Substance of walls either pink or white; 

 compartments strongly united tcith the basis; sutural edges of radii feebly 

 crenulated or smooth ; basis solid or porous. Fiist pair of cirri with de- 

 cidedly unequal rami, the segments of the shorter ramus protuberant. 

 Splnules, when present on the later cirri, are not numerous. Maxillce 

 hare an enlarged loiver pair of spines. 

 b\ Spur of the tergum very short and broad, half the width of the valve; 

 scutum strongly striate longitudinally, with a strong adductor ridge. 



Entirely white; basis not porose B. kriigeri. 



c\ Scutum strongly striate longitudinally ; walls usually more or less 

 roseate. 

 d\ Radii rather wide. Basis porose. Scutum with a distinct adductor 

 ridge; tergum with a longitudinal furrow; median segments of 



cirri vi wider than long, with 2 pairs of spines B. amaryllis 



d.\ Radii extremely narrow. Adductor ridge of scutum rather small, 

 in the upper part of valve only ; tergum without a furrow to the 

 spur ; median segments of cirri vi longer than broad. 



c\ Median segments of cirrus vi with three parts of spines B. bimw. 



e\ Median segments with four pairs of spines B. maculatus. 



c\ Scutum finely or delicately striate longitudinally ; tergum with a spur 

 fasciole but no furrow. Walls and valves entirely white. Deep 

 water species. 

 d\ Radii narrow ; adductor ridge of scutum only feebly developed. 



B. albus. 

 d\ Radii rather wide; no adductor ridge B. tenuis. 



B. amaryllis has the subgeneric characters less fully developed than 

 the other forms. It is also the only really littoral species, and the 

 most brilliantly colored one. The colored deep-water species or 

 varieties are probably rather recent derivatives of arriaryTlis. The 

 hameri group lives only well below low-water mark. 



In addition to the species contained in the United States National 

 Museum the following East Indian forms belong to this subgenus, 

 all of them described in the report on Cirripedia of the Sihoga 

 expedition : 



Balanus himre Hoek. 13 to 31 meters. 



Balanus m,aculatus Hoek. 69 to 73 meters. 



Balanus albus Hoek. 90 to 522 meters. 



