DECAPODA. 179 



notched ; two teetli on the posterior margin, and two others 

 widely separated on each lateral muscle ; the posterior largest 

 and spiniform, and situated above the origin of the posterior 

 feet. 



The sea coast of the western departments of France produces 

 some other species, which belong to the genus Ebalia, Leach*. 

 All the remaining ones are from India and America. 



Some fossil Leucosire are found in the East Indies. Three 

 species have been described by M. Desmarest, two of which, 

 according to him, are true Leucosice, Leach, and which are 

 now living in the same countries, and peculiar to them. 



Our fifth section, that of the Trigona, is composed of those species 

 whose shell is usually triangular or subovoid, narrowed before into a 

 point or kind of beak, generally uneven and rough, with lateral eyes. 

 The interval comprised between the antennae and the buccal cavity 

 is always nearly square, as long, or almost as long, as broad. The 

 claws, at least those of the males, are ahvays large and elongated. 

 The following feet are very long in a great number, and sometimes 

 the two last even differ in form from the preceding ones. The third 

 joint of the external foot-jaws is always nearly square or hexagonal, 

 in those at least whose feet are of the ordinarv length. 



The apparent number of the caudal segments varies. In both 

 sexes of several it is seven ; in others, however, the males at least, it 

 is less. 



Several of these Crustacea are designated by the vulgar appellation 

 of Ay-aignees de mer or Sea-spiders. 



Although the species of this tribe are very numerous, but two 

 have as yet been discovered except in a fossil state, one of which at 

 least — Maia squinado — exists at the present day in a living state, and 

 in the same localities f . 



A first division will comprehend those whose second and foUoAving 

 feet are similar, and which diminish progressively in size. 



From the latter we will form a first group of all those where the 

 tail, either in both sexes, or in the females alone, is composed of seven 

 segments. The third joint of the external foot-jaws is almost 

 always square, and truncated or notched at the superior internal 

 angle. 



Very large claws, particularly so Avhen compared with the other 

 feet, which are extremely short, directed horizontally and perpendi- 

 cularly to the axis of the body, as far as the carpus or joint immedi- 

 ately preceding the hand, then reflected anteriorly on themselves with 

 the fingers bent, suddenly forming an angle ; very short ocular pedi- 

 cles, projecting but little, if at all, from their cavities ; a stony and 

 very uneven or spiny shell, designate the 



Parthenope, Fab. 

 The lateral antennae of some are very short, not exceeding the 



^ * Malac. Brit., xxv. 



t See Desmar., Hist. Nat. des Crust. Foss, 



