50 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



1778. Balamis Emanuel da Costa, Historia Naturalis Testaceorum Biitanni83, 



p. 248; type by tautonymy, Balanus porcatus da Costa rew name for Lepas 



halanus Linnaeiirf. 

 1852. Monolopus Kleiu, Morch, Catal. YolcU, p. 67 {M. halanus Linnaeus here 



selected as type). 

 1854. Balaniis auct., Darwin, Monograph, p. 177. 

 1913. Ortho-Balanus Hoek, Siboga-ExYyeditie, MonograpHe 316, p. 158 (Balanus 



amphitrite here selected as type). 



Compartments six, usually having radii, except the carina; sheath 

 differentiated from rest of the inner wall. Scutum and tergum inter- 

 locked. 



Type. — Balanus halanus (Linnaeus). 



The genus Balanus in its Darwinian limits comprises species in 

 very diverse stages of evolution. Highly evolved stocks, such as 

 Megabalanus and the amphitrite group of Balanus, coexist with rela- 

 tively primitive stocks, hke Solidobalanus and Austrohalanus. It 

 may be that the groups now ranked as subgenera will in future be con- 

 sidered generic ; but I do not think this step can properly be made at 

 present, if at all. A careful study of the Austral Balani, of Conopea, 

 and of certain forms partaking of the characters of more than one 

 subgenus must be carried out before the desirability of dismember- 

 ing Balanus can be considered intelligently, liecognition of the fact 

 that pores in the wall may sometimes be closed by secondary filhng 

 does away with some apparent anomalies, but the difficulties men- 

 tioned by Darwin ^ have by no means been overcome, especially in the 

 case of Conopea. 



For convenience, and from force of habit, modern authors have 

 retained Acasta as a genus separate from Balanus; but it is now clear 

 that Darwin's misgivings on this point were well foimded. The dis- 

 tinctions in the cirri, formerly thought to exist, have been broken 

 down; and it is now known that Acasta has no higher rank than some 

 of the groups still considered to be subgenera of Balanus. 



It is a remarkable testimony to Darwin's insight and restraint that 

 every one of the species of Balanus admitted by him is still accepted 

 as vahd. Vast collections from coasts but scantdy represented in 

 his collection, or not at all, have confirmed his specific distinctions. 



The older conchologists, up to and including Lamarck, defined and 

 figiu-ed a large number of species of Balanus by external characters 

 only. Most of these can never be recognized; but the Lamarck col- 

 lection at Geneva should be gone over and his species elucidated. 

 As many are without opercular valves, this could only be done by 

 one thoroughly acquainted with the species. 



1 Monograph, pp. 190, 191. 



