THE SESSILE ilAKJSIACLES. 51 



KEY TO SUBGENEUA OF BALANU8. 



a 1 . Parietes permeated by pores. 



b l . Radii well developed, permeated by pores parallel to the basis. 



Mcgabalanus , p. 51. 

 b 2 . Radii not porous, rarely wanting. 

 c 1 . Basis calcareous, boat-shaped, elongated in the carino-rostral axis. 



Conopea, p. 234. 

 c 2 . Basis calcareous; parietes vertically ribbed within, at least near the base. 



Balanus, p. 77. 

 c 3 . Basis membranous; parietes smooth or with reticulated ridges within; rostrum 



not especially lengthened Semibalanus, p. 182. 



a 1 . Parietes not permeated by pores, solid. 

 ft 1 . Basis membranous; rostrum much longer than the other compartments. 



Membranobalanus , p. 229. 

 6 2 . Basis calcareous, boat-shaped or oblong, only a small part of it attached. 



Conopea, p. 234. 



b 3 . Basis calcareous, normally flat and attached throughout. Form normal. 

 c 1 . Radii wanting; tergurn with a long spur, but no external furrow. No spin tiles 



on the segments of the cirri Metabalamis, p. 200. 



c 2 . Radii more or less distinctly developed. 



d 1 . Tergum with the spur short, J to as wide as the base, its end truncate par- 

 allel with the base; fourth cirri having some segments armed anteriorly 

 with recurved teeth. Small, solid barnacles, smooth or sharply ribbed. 



Armatobalamis, p. 22G. 

 (P. Spur of the tergum narrower; cirrus iv without recurved teeth. 



e l . Scutum with crests for the lateral depressor muscles, and a long, strong, 

 adductor ridge; internal basal edge of parietes roughened with irregu- 

 lar points and ridges (or in B. vcstitus, strongly ribbed). Often large, 



and usually colored Austrobalanus, p. 218. 



e 2 . Scutum without crests for the depressor muscles: basal edge of parietes 



merely ribbed inside. 



f 1 . Spur rounded distally, curving into basal margin; tergum externally flat 

 or with a shallow furrow without infolded sides, not bounded by im- 

 pressed lines; scutum not much thickened within; a row of spines on 

 lower side of mandible, which has acute lower teeth. Small or minute, 

 solid barnacles, smooth or with low, broad ribs. .Solidobalanus, p. 220. 

 f 2 . Scutum ridged between adductor scar and the high articular ridge; 

 tergum with strong articular ridge, and no external furrow; lower 

 teeth of mandible short, obtuse, its lower edge hairy. Rather small, 



whitish barnacles Hespcribalanus, p. 192. 



f 3 . Scutum not conspicuously ridged within; tergum with an external 

 furrow, or a spur-fasciole bounded by lines; lower teeth of mandible 

 acute, the lower edge harry. Barnacles of moderate or large size, 

 colored or white Chirona, p. 203. 



Subgenus MEGABALANUS Hoek. 



1854. Balamis, Section A, DARWIN, Monograph, p. 194. 



1913. Mcga-Balanus HOEK, ^'fto^a-Expeditie, Monographic 316, p. 158. 



Balani having the parietes, basis and radii permeated by pores. 

 Type. Balanus tintinnabulum (Linnaeus). 



