162 CUUSTACEA. 



terminates in two very short filaments. The ocular pedicles are 

 generally longer than those of the Decapoda Macroura. The aini- 

 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 shorter 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 gemis, 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. 



t See general observations on the Decapoda. 



X 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 Nalurelles dti Regne Animal. The Quadrilatera compose our 

 first tribe, at the head of which are the Onjpoda and other Land-Crabs, ending with 

 the River-Crabs, or the Telphusa. 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 antenna; are always very short, and 

 the third articulation of whose foot-jaws is triangular, and frequently entire, or 

 Vi'ithout any emargination ; such are the Hepati, Matuta, Ovithyia, and Mursia. 



Brachyiira 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 hair)', such as the T/iiVr, Pirimelre, and Atelecycli, will immediately precede 

 these latter subgenera. As the Telphusse seem to be connected with the Eriphiae 

 and the Pilumni, 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 Orbicdlaria, the Triangularia, 

 and the NOTOPODA. But of these the Dro?HJtf and the Dorippes should be placed 

 higher in the scale. The Homaltr, 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 Homolae 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 subgeneric sections. 



