THEIR RANK. 17 



that it leads, more plainly than some other Cirripede, into 

 ordinary Crustaceans. Moreover, a great range of structure, 

 as we shall soon briefly show, is included within the group : 

 I can adduce three or four undoubted Cirripedes, very 

 considerably more different from each other, than any two 

 members within the sub-class Podophthalmia, or within the 

 Edriophthalmia, or the Branchiopoda, and quite as different 

 as within the Entomostraca. 



The opinion here expressed, that Cirripedes form a 

 sub-class of equal value with the other main Crustacean 

 groups, I am well pleased to find, accords with Mr. Dana's* 

 view, who remarks that this sub-class " has so many 

 peculiarities of structure, that it should be regarded as 

 a distinct type, rather than a subordinate division of the 

 third (or Entomostracan) type." M. Milne Edwards,t 

 after dividing all Crustacea into two groups, divides one 

 of them into four legions ; and of one of these, the 

 Entomostraca, he makes the Cirripedes a sub-group. I 

 feel so entire a deference for any opinion on affinities or 

 classification expressed by Milne Edwards, that I differ 

 from him with the greatest hesitation. He does not give 

 his reasons for assigning so subordinate a rank to Cirripedes, 

 but I imagine it is from the nature of their metamorphoses: 

 but if this be the case, I cannot understand why he should 

 assign to his Branchiopods a rank equal to his Ento- 

 mostracan s. Moreover, I must repeat, that I do not 

 believe that the larvae do resemble the larvge of Ento- 

 mostracans and Branchiopods nearly so closely as at first 

 appears to be the case. I may add, that BurmeisterJ 

 has assigned to the Cirripedes a place amongst the 

 Crustacea, almost equally subordinate to that given to them 

 by Milne Edwards. 



That Cirripedes have some special affinity to the Ento- 

 mostraca, may be inferred from the fewness of the cephalic 

 appendages, the biramous legs, the state of the abdomen, 

 and the form of the carapace. Perhaps in the peculiar 

 state of confluence of the lower segments of the gnathites, 



* 'Crustacea: United States Exploring Expedition,' p. 1407, 1852. 

 f 'Annales des Sciences Nat.,' torn, xviii, p. 120, 1852. 

 % 'Beitrage zur Naturgeschichte der Rankeuiusser,' 1831. 



2 



