HARPACTICIDA. 3 
be looked upon as the typical form of the family ; the 
genera which depart from this rule being Zaus, 
Peltidiwn, Porcellidiwm, Idya, and Scutellidiwm, all of 
which are to a greater or less extent flattened from 
above downwards. Amymone, on the other hand, 
presents a peculiarity of the opposite kind, being flat- 
tened laterally. The two pairs of antenne do not 
present any remarkable abnormalities of structure ; 
the mandibles, however, vary very considerably, more 
especially as to the degree of development of the palp, 
which in some cases is reduced to very small dimen- 
sions (Canthocamptus, Aitheyella, Laophonte, &c.) ; 
the maxille also vary a good deal in development, and 
in Longipedia approach very nearly to the shape of the 
same organs in the Calamde. The usual digitate, sub- 
triangular shape of the first pair of foot-jaws is lost in 
some genera, as in Hetwnosoma, Idya, and Scutellidium, 
where these limbs are prehensile and clawed; the second 
foot-jaw constantly takes the form of a powerfully 
clawed prehensile hand except in the genera Longipe- 
dia, Hetinosoma, Zosime, and Bradya (sub-family Longi- 
pedune), where it approaches somewhat to the structure 
seen in Calanide and Cyclopide. The first pair of feet 
has in general one or both branches adapted for 
prehension, and more or less powerfully clawed; but 
in the genera belonging to the sub-families Longi- 
pediine, Tachidune, and Amymonine, it is formed for 
swimming, being nearly or quite like the following pairs. 
The second, third, and fourth pairs are always natatory 
organs, and the outer branches are always 3-jointed ; 
the inner branch, however, has a variable number of 
