ORDER DECAPODA. 
187 
The two anterior claws are larger ; the lateral leaves of the 
fin terminating the tail are in the form of an inverted triangle 
or broader at the posterior edge. The intermediate, on the 
contrary, grow narrow from the base to the end, and proceed 
into a point. 
Callianassa, Leach , 
Have the claws very unequal, as well both in form as propor- 
tions; the carpus of the largest of the two anterior is trans- 
verse, and forms with the forceps a common body. The same 
articulation of the other claw is elongated. The two posterior 
feet are almost didactylous. The external leaf of the lateral 
fins of the end of the tail is larger than the internal, with a 
crest or ridge ; this last is even. 
The ocular pedicles are in the form of a scale or shell, and 
the cornea is situated near the middle of their external edge. 
The threads of the middle antennas are but little longer than 
their peduncle. ( Callianassa subterranea , Leach.) 
Axitjs, Leach , 
Differ from them in their claws, which are almost equal, and 
in which the carpus makes no part of the forceps ; the pos- 
terior feet are similar to the preceding. The leaves of the 
lateral fins are almost of the same size, and have each a 
longitudinal crest; the threads of the middle antennae are 
evidently longer than their peduncle. ( Axius stirhynchus , 
Leach.) 
Our second, and last subdivision, presents Crustacea, in 
which the six anterior feet form so many claws, terminating 
in a forceps perfectly didactylous, a character which dis- 
tinguishes them from all the preceding decapods, and which 
approximates them to the first of the following section ; but 
here the claws of the third pair are the largest, instead of 
which, in the others, it is the first two, and their thickness, 
