68 CRUSTACEA. 



rounded. The two filaments of the mediate antennas are much 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 forceps of whose 

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

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

 norwegicus, 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 Europe and in 

 the Mediterranean. 



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

 thing but 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 water species, the genus Astacus^ 

 properly so called, of the same author. 



Astacus marinus, Fab.; Cancer gammarus, L.; Herbst., 

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

 point 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 other is elongated, 

 and has numerous small ones. Old individuals are 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 has been carefully studied by Messrs Victor Andouin, 

 and Milne Edwards. 

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

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

 of the tail, or the middle one of its terminal fin, is transversely di- 

 vided by a suture. The 



Astacus communis; Cancer astacus, L.; Roesel, Insect., Ill, liv, 

 vii. The Craw-Fish has its anterior forceps granulated, and 

 the inner edges finely dentated. There is a tooth on each side 

 of the snout, and two at its base; the lateral edges of the seg- 

 ments of the tail form an acute angle. Its colour, which is 

 usually a greenish brown, is sometimes altered by accidental 

 circumstances. 



This species, which inhabits the fresh waters of Europe, has 

 been more particularly studied, both as respects its anatomy 



