190 



F,AL\\II).F,. 



each successive exuviation: the pedicels of the cirri are long 

 in proportion to the rami at this same early age.* 



Notwithstanding the difficulties now enumerated, I hope 

 that, owing to having examined a vast number of specimens 

 of the most varying species, I have not fallen into very 

 many errors. I have endeavoured to err on the side of 

 making too few instead of too many species. In those 

 cases, however, in which I have seen only a few specimens, 

 I have been sometimes compelled to decide without sufficient 

 evidence. 



I would gladly have divided this genus, already including 

 45 species, into smaller genera; but so far from being 

 enabled to do so, I have been compelled to form my Sections 

 (immediately to be given) on characters not absolutely in- 

 variable, and far from obvious. I was particularly anxious 

 to separate the elongated species with a boat -formed basis, 

 which are attached to Gorgoniae, and which form the genus 

 Conopea of Say, but I was unable to effect their separation 

 even as a sub-genus ; for B. navicula and cymbiforruJx 

 graduate in the most insensible manner through B. galeahis 

 (the type of Say's genus) and B. calceolus into B. stultus, and 

 this into B. Ajax ; yet this latter species has even been 

 described as a mere variety of the typical B. tintinnabidum ! 

 Indeed, so insensible is this graduation, that the first and 

 second sections of the genus are hardly distinct. I fully 



* In some specimens of Balanus perforatus I made the following enumeration 

 of the number of segments in the cirri : — 



In the specimen |th of an inch in basal diameter, each segment of the poste- 

 rior cirri carried five pairs of spines ; whereas, in full-grown specimens, there 

 are six or seven pairs. In the 5 ' Q th of an inch specimen, on the inner maxillae, 

 there were no spines between the upper large and the lower large pair of 

 spines ; whereas, in the \t\\ of an inch specimen, there were five intermediate 

 spines, and in larger specimens nine or ten spines. 



