B ALAN us. 



Balaniis et Acasta, Leach. Balaims^ Ldm. 



TESTA conica, saepe elongato-conica, valvis 

 senis, inaequalibus, lateraliter ferruminatis, 

 composita; apice pervio, basi valva testacea, 

 adhaerente clausa: valvse, antica, postica, et 

 dua? ex lateralibus majores. Operculum bipar- 

 titum, valvis quatuor compositum ; pari postico 

 prominulo. 



Specierum spongias incolentium, basis pocil- 

 lum vel patellam referens ; Gorgoniis affixarum 

 plerumque elongata lanceolata. 



We have already expressed our approbation of the general 

 outline of an arrangement of the Cirripedes^ published by 

 Leach in the " Supplement to Encyclopaedia Britannica;'* 

 nevertheless, upon reconsideration, we do not entirely 

 concur with him in separating those species which inhabit 

 sponges, and to which he has given the name of Acasta, 

 from the other Balani, which he has done merely on ac- 

 count of their (generally) cup-shaped base ; the reason for 

 our dissent is, and we think it very conclusive, that we 

 possess specimens of a Balanus in sponge, whose base is 

 as flat as those of the common Balani generally are ; and 

 further, the slightest examination will prove that the 

 bases of ail these shells are subject to great variation, and 

 that in all cases they conform themselves to the substance 

 to which they are attached, and to the circumstances in 

 which they are placed. We have observed a remarkable 

 instance of this in a small Balanus that has lately been 

 discovered on a Gorgonia ; where an individual attached 

 to the stem has the common form of a Balanus, and ano- 

 ther individual which is placed on one of the slender 

 branches has a deeply hollow and much elongated base. 

 We therefore have re-united Acasta to Balanus, 



