DECAPODA. 69 



and habits, and the faculty enjoyed by the Crustacea of regene- 

 rating their antenae and feet when they are either mutilated or 

 destroyed. When about to cast its shell, two stony concretions 

 are found in the stomach, formerly much used in medical prac- 

 tice as an absorbent, but now replaced by the carbonate of mag- 

 nesia. It conceals itself in holes, or under stones, never quitting 

 its retreat except to search for food, which consists of small 

 Mollusca and Fishes, and the larvse of Insects. It also feeds on 

 putrid flesh, the carcases of quadrupeds, for instance, which 

 are placed as a bait for them in nets, or in the centre of fagots 

 of wood. They are also taken in their holes by the light of 

 torches. It changes its shell towards the end of spring. Two 

 months after coition, which takes place ventribus junctis, the 

 female produces her ova, which are at first collected in masses, 

 and glued to the false feet by means of a viscid humour. They 

 are of a reddish brown colour, and enlarge before they are 

 hatched. The young Astaci, at first extremely soft and precisely 

 like their parent, shelter themselves under her tail and remain 

 there several days, until their bodies acquire a certain degree of 

 solidity. 



The term of existence assigned to the Astaci seems to be 

 twenty years and upwards, their size augmenting in proportion 

 to their age. Those are preferred'for the table which inhabit 

 running streams of fresh water. A parasitic animal belonging 

 to the Annelides, is found on their branchise, long ago observed 

 by Rcesel, but imperfectly known until the researches of M. 

 Odier(l). 



The fresh-waters of North America produce another species, 



the A. Bartonii, figured by Bosc. Hist. Nat. des Crust., II, x, 1. 



A third inhabits the rice-fields of the same country, to which, 



according to Major Le Conte, one of the best naturalists of the 



United States, it is very injurious. 



In the fourth section, that of the Carides, the intermedial anten- 



nje are superior or are inserted above the laterals: the peduncle of 



these latter is completely covered by a large scale. 



Their body is arcuated, almost gibbous, and of a less solid con 

 sistence than that of the preceding Crustacea. The front is always 

 drawn out into a point, and most frequently so as to resemble a ros- 

 trum or pointed lamina compressed and dentated along the edges. 



(1) See his Memoire sur le Branchiodelle, inserted in the Mem. de la Soc. d'Hist. 

 Nat. tome I, p. 69, et seq. 



