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useful these great folding- doors, with their dense armature of 
bristles, must be in the reception of morsels made up of fine, 
loose particles, merely pressed together. 
The mandibles, also, are very remarkable. Quite recently 
it has been put forward, as a distinctive character between the 
Long- tailed Decapods and the Mysidae, that ‘ the right and left 
mandibles are similar in the Macrura, dissimilar, and often 
very different, in the Mysidae/ Even leaving Atyoida out of 
the question, this supposed distinction will not hold good (in 
the Palaemonidae, for example, the tubercles of the masticatory 
processes are quite different to the right and left) ; but nowhere 
else among the Macrura have I seen so great a difference between 
the two mandibles as in our Atyoida , where it strikes one at the 
first glance. I would regard this as an old inherited character 
rather than as a recent adaptation, more especially seeing that 
in other respects, also, the mandibles show an ancient form. 
In those Prawns which have retained to the present day the 
most complete and original developmental history, the man- 
dibles, at their first appearance in the interior of the third pair 
of limbs of the Nauplius, show an apical part armed with 
cutting teeth, a manducatory process furnished with transverse 
ridges behind this, and between the two a series of bristles ; 
and we find the same three parts in Atyoida. Such mandibles 
are nowadays rare among the Decapoda, but frequent in 
others of the higher Crustacea, such as the Amphipoda and 
Cumacea. 
The two pairs of feet which follow the chelae (the third and 
fourth thoracic limbs) are slender walking limbs, the last joint 
of which is armed with from six to nine curved, claw-like 
spines, such as are also met with in other Prawns (e.g. Hippo - 
lyte ), which, like our species, are fond of clinging to plants. 
The last or fifth pair of limbs is also employed in walking and 
clinging, and has a few curved spines at the end of the finger ; 
but in addition to these, the lower edge of the finger bears a 
delicate comb, employed especially in cleansing the abdomen. 
A systematic cleansing of the abdomen is performed by the 
animal with great care and deliberation, and occupies several 
minutes. It commences with the first pair of swimming feet, 
the four following ones being for the time laid back ; when 
the first pair and the space between the first and second is 
clean, the second pair comes up, then the third, and so on. 
Last of all, it comes to the turn of the tail, which has to bend 
very much forward in order to come within reach of the comb. 
Neither the two anterior pairs of limbs, the hands belong- 
ing to which, with their long bristles, may occasionally be seen 
sweeping about the fore part of the body, nor those of the last 
pair, are adapted to penetrate into the branchial cavities and 
