160 CRUSTACEA. 



bits transverse colls formed by crustaceous laminae, and separated in 

 their middle by a longitudinal range of the same nature. 



The sexual organs of the male are situated near the origin of the 

 two posterior feet. Two articulated pieces, of a solid consistence, 

 and resembling horns, stylets, or setaceous antennae, placed at the 

 junction of the tail with the thorax and replacing the first pair of 

 subcaudal appendages, are regarded as the male organs of copulation, 

 or at least as their sheaths. But, according to our observations on 

 various Decapoda, each of them consists of a little membranous body, 

 sometimes setaceous, and at others filiform or cylindrical, that pro- 

 jects from a hole situated at the articulation of the hip of the two 

 posterior feet, with the lower shell. The two vulvae are placed on 

 this piece, between those of the third pair, or on their first joint, a 

 disposition depending on the widening and narrowing of the lower 

 shell. Copulation takes place, venire a venire. These animals grow 

 but slowly, and live a long time. It is among them that we find the 

 largest and most useful species, but their flesh is not easily digested. 

 The body of some Palinuri attains the length of a metre. Their 

 claws are efficacious weapons, and have such power in large indivi- 

 duals, that they have been seen to seize a goat, and drag it from the 

 shore. They usually inhabit water, but do not instantly perish when 

 deprived of it; some species even pass a part of their lives on land, 

 only visiting the water in the nuptial season, and for the purpose of 

 depositing their spawn. Even they are compelled to fix their domicile 

 either in burrows, or in cool, damp places. The Decapoda are vora- 

 cious and carnivorous. Certain species even penetrate into ceme- 

 tries, and devour the dead. Their limbs are regenerated with sur- 

 prising promptitude, but it is requisite that the fracture be at the 

 junction of the articulations, and when accident determines it other- 

 wise, they know how to apply a remedy. When they wish to change 

 their skin, they seek a retired and solitary spot, in order to be shel- 

 tered from their enemies, and to remain at rest. When the change 

 is effected, their body is soft, and has a more exquisite flavour. A 

 chemical analysis of the old shell proves it to be formed of the car- 

 bonate and phosphate of lime, united in different portions with gela- 

 tine. On these proportions depends the solidity of the shell : it is 

 much less thick and flexible in the latter genera of this order, and 

 further on, it becomes almost membranous. M. de Blainville has 

 observed that the shell of the Palinurus is composed of four superin- 

 cumbent layers, the superior and two inferior of which are mem- 

 branous ; the calcareous matter is interposed between them, forming 

 the fourth. Exposed to heat, the epidermis becomes of a more or 



