THE SESSILE BARNACLES. 49 



Siabfamily BAH.A.JS'IN'.^E; Darwin. 



1854. BalaninXj First Section, Darwin, Monograpli, p. 175 (exclusive of Chelon- 

 obia). 



Opercular valves together as large as the orifice ; scuta articulated 

 with the torga. Sheath distmctly difrcrontiatocl from and shorter 

 than the inner widl of the body-chaml^cr, its lower edge not cut 

 into teeth. 



KEY TO GENERA OP BALANIN^ AND CHELONIBIIN.'B.l 



a'. ( "ompartments bix. 

 6'. Opcrciilar valves mucli narrower than the orifice, the ecutiim united to the 

 tergimi by a chitinous articular ridge; walls porous, or septate at the base; 

 sheath, forming the whole inner wall, deeply notched or reduced to slender 



pillars at the base; basis membranous Chelonihin, p. 262. 



b^. Opercular valves together as wide as the orifice; sheath differentiated from and 

 shorter than the inner wall. 

 c^. Eadii wanting or very weakly, indistinctly developed; compartments not 

 porose. 

 tP. Alee conspicuous externally. 



eK Basis calcareous PachyJasma, p. 327. 



e^. Basis membranous, at least in part ITexclasmn, p. 329. 



dP. Sutures narrow, the ala; not conspicuous externally Bnlnnus, p. 49. 



(?. Radii developed; or if wanting, the compartments are porose. .Balanus, p. 49. 

 (Basis calcareous, cup-shaped, or flat; compartments thin, not porose, 



weakly connected; living imbedded in sponges Acasta, p. 241.) 



a?. Compartments four, or by calcification of the sutures, imited into one piece. 



h^. Wall conspicuously porose, the sutures visible, at least inside. Tciradita, p. 248, 

 6^. Wall-corn partmcnta not porose. 

 c^ Bads membranous; four compartments; sessile, on rocks, etc., littoral. 



Elminius, ]■>. 260. 

 c^. Basis membranous, produced in fonn of a short pedimcle; wall comimrtmenta 



concrescent into one, as in Pyrgoma Pyrgojjsis? 



(?. Basis calcareous, cup-sliaped, oi cylindric; growing on corals and millepores. 



d. Four compartments, with nidii Creusin, p. 261. 



d^. Compartments concrescent into one Pyrgoma, p. 261. 



Genus BALANUS E. da Costa. 



1758. Lepas Linn.eus, Systema Natune, ed. 10, p. 667, in part, and of most 



early authors. 

 1763. Balaniis Gronovius, Zoophylacii Gronoviani, p. 257.^ 



' For obvious considerations of convenience, this key takes account of the hard parts only. It is therefore 

 somrwhat artificial, since provision had to be made for Pachylasma and Ilcidasma, pencra of Chthamalidte 

 which resemble Balanidffi superficially, but diilor fundamentally by the shape of the labrura, etc. 



^ Pyrgopsis Gruvel, 1907. Mem. Asiatic Soc. of Bengal, vol. 2, No. 1, p. 8, for P. annandalci Gruvel, 

 Andaman Islands, on reef. The single species of this genus is not contained in the National Museum. 



' Gronovius was the first post-Lirma2an author to divide the Linnaean genus Lepas. lie established 

 the genus Balanus for several species of Balanus and Chclonibia. I nominate his species No. 1077 as the 

 type. This is identical with Balanus balanus Linnaeus. 



Gronovius was not a binomial author, except m some pages of tabularvm cxplicatio at the end of his 

 work, but his nomenclature was "binary." His genera were properly proposed, but his species, with 

 the exception already noted, are not named, but are indicated by phrasi-s. Accordnig to the ruling of 

 the International Conimittee on Nomenclature— which I think was in a high degree injudicious — the 

 genera of Gronovius are to be accepted. 



