ORDER DECAPODA. 
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The fifth section, that of Trigona, is composed of species 
whose testa is generally triangular or subovoid, narrowed into 
a point, or in the manner of a beak in front, usually very un- 
equal and rough, and the eyes are lateral. 
The epistoma,or interval comprised between the antennae and 
the buccal cavity, is almost always square, as long, or almost 
as long, as broad. The claws, or at least those of the males, 
are always broad and elongated. The following feet are very 
long in a great number, and sometimes even the last two 
have a different form from the preceding. The third articula- 
tion of the external jaw-feet is always square or hexagonal, in 
those at least, whose feet are of the usual length. 
The apparent number of the segments of the tail varies. 
In many of them it is seven in both sexes ; but in others, or 
at least in the males, it is less. 
Many of these Crustacea have been vulgarly designated 
under the collective name of Sect-spiders . 
Although the species of this tribe are very numerous, but 
two have as yet been discovered in the fossil state, and one 
of which (Maia squinado) is still existing in the same 
localities. 
A first division will comprehend those, whose second and 
following feet are similar, and the size of which diminishes 
progressively. 
Among those we shall form a first group, of all the species 
whose tail, either in both sexes, or in the females, consists of 
seven articulations. The third articulation of the external 
jaw-feet is always square, and truncated or emarginated at 
the upper internal angle. 
Very large claw T s, especially when compared with the other 
feet, which are very short, directed horizontally, and per- 
pendicularly to the axis of the body, as far as the carpus or 
articulation preceding the hand, afterwards folded in front 
