T11E SESSILE BARNACLES. 49 



Subfamily B^LA.JVriNJE Darwin. 



1854. BalaniniK, First Section, DARWIN, Monograph, p. 175 (exclusive of Chelon- 

 obia). 



Opercular valves together as large as the orifice; scuta articulated 

 with the tcrga. Sheath distinctly differentiated from and shorter 

 than the inner wall of the body-chamber, its lower edge not cut 

 into teeth. 



KEY TO GENERA OF BALANIN^! AND CHELONIBIIN^E. 1 



a 1 . Compartments bix. 



b 1 . Opercular valves much narrower than the orifice, the scutum united to the 

 tergum 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 .................... Chclonibia, p. 262. 



6 2 . Opercular valves together as wide as the orifice; sheath differentiated from and 



shorter than the inner wall. 

 c 1 . Radii wanting or very weakly, indistinctly developed; compartments not 



porose. 



d 1 . Alse conspicuous externally. 

 e 1 . Basis calcareous ............................... ... .Pachylasma, p. 327. 



e 2 . Basis membranous, at least in part .................... ITcxelasma, p. 329. 



d 2 . Sutures narrow, the alee not conspicuous externally ......... Balanus, p. 49. 



c 2 . 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 2 . Compartments four, or by calcification of the sutures, united into one piece. 



& 1 . Wall conspicuously poro&e, the sutures visible, at least inside. Tetraclita, p. 248. 

 b 2 . Wall-compartments not porose. 

 c 1 . Basis membranous; four compartments; sessile, on rocks, etc., littoral. 



Elminius, p. 260. 



c 2 . Basis membranous, produced in form of a short peduncle; wall compartments 

 concreecent into one, as in Pyrgoma ............................ Pyrgnpsis. 2 



c 3 . BasiiS calcareous, cup-shaped, or cylindric; growing on corals and millepores. 

 d. Four compartments, with radii .......................... Creusia, p. 261. 



d 1 . Compartments concrescent into one .................... Pyrgoma, p. 261. 



Genus BALANUS E. da Costa. 



1758. Lepas LINN.EUS, Systema Naturae, ed. 10, p. 667, in part, and of most 



early authors. 

 1763. Balanus GRONOVIUS, Zoophylacii Gronoviani, p. 257. 3 



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

 somewhat artificial, since provision had to be made for Pachylasma and Hcxdasma, genera of Chthamalidie 

 which resemble Balanidre superficially, but differ fundamentally by the shape of the labruru, etc. 



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

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



3 Gronovius was the first post-Linnsean author to divide the Linnsean genus Lcpas. He 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 Linnscus. 



Gronovius was not a binomial author, except in some pages of tabular um explicatio 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 phrases. According to the ruling of 

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

 genera of Gronovius are to be accepted. 



