DECAPODA. 201 



Eryon, Desniar., 



All the leaflets of tlie caudal fin are narrowcrl at their extremity 

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

 suture. The two filaments of tlie mediate antennee are very short, 

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

 deeply eniarginated. 



I'lie forceps of the two anterior claws are narrow and elongated. 



This subgenus was established by Desmarcst on a fossil species, — 

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

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

 Aichtedt in the margravate of Anspach. 



AsTAcus, Gro7iov., 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 rounded. 

 The two filaments of the mediate antenn;« are mucli longer than 

 their peduncle. The sides of the shell are entire, or not incised. 



In some, all inhabiting salt water, the last segment of the tail, or 

 that which occupies the middle of the terminal fin, presents no trans- 

 verse suture. 



Those whose lateral antennae have a large scale on their peduncle, 

 whose eyes are very large and reniform, and the forcef)s of whose 

 two anterior claws are narrow, elongated, prismatic, and equal, 

 form the genus Nephrops of Leach, the type of which is the Cancer 

 norwerjicus, L.; de Geer, Insect., VII, XXI; Herbst., XXVI, 3; 

 Leach, Malac. Brit., XXVI. The two anterior claws are furnished 

 with dentated spines and ridges, and the superior surface of the tail is 

 sculptured. It is found in the seas of the north of ICurope, and in the 

 Mediterranean. 



Those in Avhich the peduncle of the lateral antennae presents no- 

 thing bvit two short projections in the form of teeth or spines, whose 

 eyes are neither large nor reniform, and whose forceps are more or 

 less oval, compose, with the fresh Avater species, the genus Astaciis, 

 properly so called, of the same author. 



Astacus marinits, Fab.; Cancer rjammaru^, L. ; Herbst., 

 XXV; Penn., Brit. ZooL, V,x, 21 ; (the Common Lobster). The 

 2)oint or rostrum of the anterior extremity of the shell has three 

 teeth on each side, and another double one at its base. The an- 

 terior claws are very large and unequal ; the largest finger of the 

 forceps is oval, with great molar teeth, the otiier is elongated, 

 and has munerous small ones. Old individuals arc sometimes 

 more than half a metre in length. Its flesh is highly esteemed. 

 It is found in the European Ocean, in the Mediterranean, and 

 even on the eastern coasts of North America. Its internal 

 structure h^s been carefully stiulied by J.Iessrs. Victor Andouin, 

 and Milne Edwards. 

 In the fresh water species, wliich otherwise resemble the preced- 

 ing in their antenns, eyes, and form of the claws, the last segment of 



