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160 A HISTORY OF RECENT CRUSTACEA 
which this genus and some of its immediate neighbours 
are distinguished from one another. 
Pagirus (in restricted sense). The ‘front’ without 
distinct rostral projection. Eye-stalks stout, with basal 
scales usually wide apart. Acicle of second antennz short 
and robust, the flagellum long and naked. The third 
maxillipeds approximate at the base. The left cheliped 
usually the larger. The fourth pair of legs chelate. 
Eupagirus, Brandt, 1851. The ‘front’ with a dis- 
tinct rostral projection. Eye-stalks stout, with basal 
scales wide apart. Acicle of second antennz long and 
slender, the flagellum long and naked. The third maxil- 
lipeds distant at the base. ‘The right cheliped usually the 
larger. The fourth pair of legs subchelate. 
Clibanarius, Dana, 1852. The ‘front’ with a distinct 
rostral projection. The eye-stalks usually slender, with 
the basal scales close together. Acicle of second antennz 
short, the flagellum naked. The chelipeds subequal and 
similar. The fourth pair of legs chelate. 
Aniculus, Dana, 1852, and Calcinus, Dana, 1852, agree 
with Clibanarius as above defined, except that Aniculus 
has the fourth pair of legs subchelate, and Calcinus has 
the chelipeds very unequal. 
Diogénes, Dana, 1852. There is a movable rostriform 
process between the eye-stalks, distinct from the rostrum. 
The acicle of the second antennz has a broad base; the 
flagellum is ciliated. The left cheliped is the larger. The 
fourth pair of legs chelate. 
When characters are set out in this way, it would 
seem that there should be little difficulty in determining 
to what genus a species belongs, but nature does not 
always lend itself very obligingly to the necessities of 
classification. Thus, in regard to Pagurus similiminus, 
Henderson, its author is obliged to say: ‘The chelipedes 
are of equal size, and in every respect similar to one 
another, belonging essentially to the form which is charac- 
teristic of the genus Clibanarius,’ and presently afterwards, 
under the species Clibanarius strigimdnus (White), Dr. 
Henderson observes: ‘As in the case of Pagurus simili- 
