Ö2 
Memoirs of the Indian Museum. 
[VoL. II 
and processes with which it is provided. No matter how the group is subdivided, 
however, it is necessary to include in each subdivision forms in which the valves have 
become degenerate in accordance with a semi-parasitic mode of life. In some cases 
it is only the dwarfed and otherwise degenerate males which exhibit this feature, while 
in others the large hermaphrodites do so. Moreover, it is necessary to recognize 
that even within the limits of a single family both divergence and convergence may 
take place in the course of evolution. It is clear, for instance, that the genera Diche- 
laspis and Conchoderma are not very closely allied to one another ; yet evolution 
has taken a similar direction in each of them, and has produced similar results, which 
are to some extent correlated with a similar mode of life. It is the fact of conver- 
gence that makes it so difficult to subdivide the group, for it is often impossible to 
say whether a similarity in any one organ or structure is due to direct phylogenetic 
relationship or to parallel evolution, while the value that is to be given to each char- 
acter is a matter that calls for the nicest discrimination — which, indeed, must always 
remain largely a matter of opinion. 
In these circumstances it seems best to build the system of classification on as 
broad a basis as possible, and, after considerable hesitation, I have decided to adopt 
that put forward in Gruvel’s Monographie des Cirrhipèdes (1905), with certain modi- 
fications rendered necessary by more recent investigations. Gruvel recognizes the 
following families and subfamilies : — 
Family I.— POLYASPIDÆ:. 
Subfamily {a). — Poi,i.icipin^ (genera, Pollicipes, Scalpelliim) . 
Subfamily {h). — Lithotrynæ; (genus, Lithotrya). 
Family II.— PENTASPIDÆ. 
Subfamily («).— Oxynaspinæ; (genus, Oxynaspis). 
Subfamily (ô). — F epadinæ; (genera, Lepas, Megalasma, Pœcilasma, Diche- 
laspis, Conchoderma). 
Family III.— TETRASPIDAÎ (genus, Ihla). 
Family IV.— ANASPIDÆ. 
Subfamily {a). — Ajlepadinæ; (genus, Alepas). 
Subfamily (b). — Aneeasminæ; (genera, Chcetolepas , Gymnolepas , Anelasma). 
In criticising this arrangement the first point to be noted is that the names are 
not altogether satisfactory. It would have been both more convenient and more 
correct to call the families Pollicipedidæ, Eepadidæ, Iblidæ and Alepadidæ. 
Apart from this, there are one or two features of the scheme that require 
alteration. Pilsbry has recently pointed out that two very distinct genera have 
hitherto been confused under the name Alepas, and has proposed for all the species 
included under this name by Gruvel except the species first described {Alepas 
parasitica) , the generic name Heter alepas. He has shown, further, that the genus 
Gymnolepas of C. W. Aurivillius is identical with Sander Rang’s genus Alepas. This 
1 “ The Barnacles (Cirripedia) contained in the collections of the U. S. Nat. Museum,” Bull. U. S, 
Nat. Mus., No. 60, p. 100 (1907). 
