THE SESSILE BAKNACLES. 51 



KEY TO SUBGENERA OF BALANUS. 



a*. Parietes permeated by pores. 



6'. Radii well developed, permeated by poTca parallel to the basis. 



Mcgahalanus, p. 51. 

 6-. Radii not porous, rarely wanting. 

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



Conopea, p. 234. 

 C-. Basis calcareous; parietes vertically ribbed within, at least near the base. 



BalaniLS, p. 77. 

 (?. Basis membranous; parietes smooth or with reticulated ridges witliin; rostrum 



not especially lengthened Scmibalantts, p. 182. 



o'. Parietes not permeated by pores, solid. 

 6'. Basis membranous; rostrum much longer than the other compartments. 



Membranobalanus , \). 229. 

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



Conopea, p. 234. 

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

 c^ Radii wanting; tergum with a long spur, but no external furrow. No spinules 



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



c^. Radii more or less distinctly developed. 

 d^. Tergum with the sijur short, J to -J 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 riljl)cd. 



Arvwtobalanus , p. 226. 

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

 e^. Scutmn 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. vestitus, strongly ribbed). Often large, 



and usually colored Austrobalanus, p. 218. 



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

 merely ribbed inside. 

 j^. 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 inandible, which has acute lower teeth. Small or minute, 

 solid barnacles, smooth or with low, broad ril)s. .Solidobalanus, p. 220. 

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

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

 teeth of mandible short, obtxise, its lower edge hiury. Rather small, 



whitish barnacles Hesperihalanus, p. 192. 



p. 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 hairy. Barnacles of moderate or large size, 

 colored or white Chiroiia, p. 203. 



Subgenus MEGABALANUS Hoek. 



1854. Balanus, Section A, Darwin, Monograph, p. 194. 



1913, Mega-Balanus Hoek, ASiftog^a-Expeditie, Monograplue 316, p. 158. 



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

 Type. — Balanus tintinnahulum (Linnaeus). 



