162 
CRUSTACEA. 
terminates in two very short filaments. The ocular pedicles are. 
generally longer than those of the Decapoda Macroura. The auri- 
cular tube is almost always stony. The first pair of feet terminate in 
a forceps or claw. The branchiae are disposed on a single range, in 
the form of pyramidal ligulae, composed of a multitude of leaflets 
piled one on another, in a direction parallel to their axis. The foot- 
jaws are generally shoi’ter and broader than in the other Decapoda, 
the two external ones forming a sort of lip *. Their nervous system 
also differs from that of the Macroura f. 
This family, as in several of the systems anterior to the distribution 
of these animals by Daldorf, might constitute but one genus, that of 
Cancer, Lin . 
In the greater number, all the feet are attached to the sides of the 
pectus, and are always exposed ; this is the case in the first five sec- 
tions. The first, or that of the Pinnipedes |, to this character, adds 
that of having the last feet, at least, terminated by a very flat or fin- 
like joint that is oval or orbicular and broader than the same joint 
of the preceding feet, even when they also are shaped like a fin. 
They seldom frequent the coast, and are generally found in the high 
seas. With the exception of the Orithyiae, we observe but five dis- 
tinctly marked segments in the tail of the males, while that of the 
* Those of the Macroura are longer and narrower. It is on this difference that 
Fabricius established his order of the Exochnata. 
p See general observations on the Decapoda. 
J This systematic arrangement of the Brachyura is artificial, or but little 
natural in some respects ; in consequence of which, we have somewhat altered it 
in our Families Naturelles du Regne Animal. The Quadrilatera compose our 
first tribe, at the head of which are the Ocypoda and other Land-Crabs, ending with 
the River-Crahs, or the Telphuste. The Arcuta form the second. That of the 
Cryptopoda appearing to us more closely allied to the preceding one than the 
Triangularia, will immediately follow, and be the third, and not the fourth, as 
in this method. Immediately after the Arcuata we will place those genera whose 
claws are in the form of a crest, whose lateral antennae are always very short, and 
the third articulation of whose foot-jaws is triangular, and frequently entire, or 
without any emargination ; such are the Hepati, Matutce, Orithyiee, and Mursice. 
Brachyura approaching the latter in the form of the same articulation, but 
whose claws differ, and where the lateral antennae are salient, advanced, and fre- 
quently hairy, such as the Thia, Pirimelee, and Atelecycli, will immediately precede 
these latter subgenera. As the Telphusse seem to be connected with the Eriphise 
and the PLlumni, and as from these we naturally pass to Cancer properly so called, 
or the Cancer, Fab., it follows that the Portuni and other natatory Arcuata should 
be at the head of this tribe. Then follow the Orbicularia, the Triangularia, 
and the Notopoda. But of these the Dromif® and the Borippes should be placed 
higher in the scale. The Homolee, Lithodes, and Ranina, appear to me to be of all 
the Brachyura, those which are most closely allied to the Macroura. The external 
foot-jaws of the Homolse and of the Lithodes greatly resemble those of the Macroura 
by their length and projection. 
Although we have divided the Decapoda into two genera only, in order to con- 
form to modern systems, and to diminish the number of subgenera, our sections may 
be converted into tribes, corresponding to as many subgenera, to be afterwards 
divided into various subgencric sections. 
