202 
CRUSTACEA. 
the tail, or the middle one of its terminal fin, is transversely divided 
by a suture. The 
Astaciis 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 
and habits, and the faculty enjoyed by the Crustacea of regene- 
rating their antennae 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 re])laced 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 larvae of Insects. It also feeds on 
putrid flesh, the carcases of quadrupeds, for instance, which 
are jjlaced 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 j)rcduces 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 branchiae, long ago observed 
by Rcesel, but imperfectly known until the researches of M. 
ddier *. 
The fresh-waters of North America produce another species, 
the A. Bartonii, figured by Bose. — 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 C!arides, the intermedial antennae 
are superior or are inserted above the laterals : the peduncle of these 
latter is completely covered l)y a large scale. 
* See his ]\Ienioire sur le Bmnchiodelle, inserted in the M(5m. de la Soc. d’Hist. 
Nat. tome I, p. C9, et seq. 
