DECAPODA. 21 



two external ones forming a sort of lip(l). Their nervous 

 system also differs from that of the Macroura(2). 



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 

 ])ectus, and are always exposed; this is the case in the first five sec- 

 tions. The first, or that of the Pinnipedes(3), to this character, adds 

 that of having the last feet, at least, terrainated 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 



(1) Those of the Macroura are longer and narrower. It is on this difference 

 that Fabricius established his order of the Exochnata. 



(2) See general observations on the Decapoda. 



(3) 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 Ocypodaa,nd other Land-Crabs, ending with 

 the River-Crabs, or the Telphusx. The Ahcuata form the second. That of the 

 Crxptopoda appearing to us more closely allied to the preceding one than the 

 Triakgularia, will immediately follow, and be the tlilrd, 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 antennx 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, Matutse, OvUhyise, and Mursix. 



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 Thise, Pirimelse, and AtdecycU, will immediately pre- 

 cede these latter svibgenera. • As the Telphusx seem to be connected with the 

 Eriphije and the I'ilumni, and as from these we naturally pass to Cancer properly 

 so called, or the Cancer, Fab., it follows that the Portuni and other natatory Ar- 

 cuata should be at the head of this tribe. Then follow the Orbicciaria, the 

 Triangularia, and the Notopoda. But of these the JDromiw and the Dorippes 

 should be placed higher in the scale. The Homobe, Lithodes, and Raninae, appear 

 tome to be of all the Brachyura, those which are most closely allied to the Mac- 

 roura. The external foot-jaws of the Homolse and of the Lithodes greatly resem- 

 ble 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 after- 

 wards divided into various subgeneric sections. 



