DECAPODA. 67 



Axius, Leach, 



Differs from Callianassa in the claws, which are nearly equal, and 

 in the carpus, which does not form part of the forceps; the posterior 

 feet are similar to the preceding ones. The leaflets of the lateral 

 fins are nearly equal in size, and have each a longitudinal ridge. 

 The filaments of the mediate antennae are evidently longer than their 

 peduncle. The 



Axius stirhynchus, Leach, Malac. Brit., XXXIII, is found 

 on the coast of England, and on that of the western depart- 

 ments of France, where it was observed by M. d'Orbigny, sen., 

 a corresponding member of the Mus. d'Hist. Nat. 

 Our second and last subdivision consists of Crustacea whose six 

 anterior feet form as many claws, terminating in a perfectly didac- 

 tyle forceps, a character which distinguishes them from all the pre- 

 ceding Decapoda, and one which approximates them to the first of 

 the ensuing section; but here the claws of the third pair are the 

 largest, whereas there, it is the two first, besides which they are 

 much thicker. The peduncle of the lateral antennae is accompanied 

 by a scale or spines. The external leaflet of the lateral fins at the 

 end of the tail, in all the living species, is divided in two by a trans- 

 verse suture(l). In the 



Eryon, Desmar., 



All the leaflets of the caudal fin are narrowed at their extremity 

 and terminate in a point; the external one presents no transverse 

 suture. The two filaments of the mediate antennse are very short, 

 and hardly longer than their peduncle. The sides of the shell are 

 deeply emarginated. 



The forceps of the two anterior claws are narrow and elongated. 



This subgenus was established by Desmarest on a fossil species, 

 Eryon Cuvieri, Hist. Nat. des Crust. Foss., X, 4; Consid. XXXIV, 

 3, found in a lithographic, calcareous stone from Pappenheim and 

 Aichtedt in the margraviate of Anspach. 



Astacus, Gronov., Fab. 



Leaflets of the lateral fins at the end of the tail widened and 

 rounded at their extremity; the external one divided transversely by 

 a suture, and the posterior extremity of the mediate obtuse or 



(1) This character is common to the following section, so that by it we might 

 divide the Macroura, the Schizopoda excepted, into two great divisions. 



