102 CRUSTACEA. 



numbers which are annually consumed are caught. It is 

 distinguished generically from the cray-tish by the middle 

 lamella of the tail being composed of a single piece, and by 

 the sides of the abdominal segments being obtuse. 



The cray-fish forms the genus Potamobius of Leach, al- 

 though Desmarets and others unite it v\ith the lobster in the 

 genus Astacus. 



The cray-fish is found in the fresh Avaters of Europe and the 

 north of Asia. It secretes itself under stones and in holes in the 

 banks, from -which it only conies forth to take its food, which 

 consists of molluscous animals, small fishes, and decaying animal 

 matter. It is said to attain the age of twenty years, its size 

 gradually increasing all the time, as each year, at the end of 

 the spring, it sheds its outer covering, shortly after which it is 

 found incased in a fi-esh coat as firm as the old one, and much 

 enlarged, sometimes having increased as much as one-fifth in its 

 size. 



The female deposits her eggs two months after impregnation : 

 these she retains for a considerable time beneath her abdomen, 

 keeping them in such situation by means of a viscid matter with 

 which they are covered, and by which they are attached to the 

 false or swimming legs, with which this part of the body is fur- 

 nished in its under surface. These eggs increase in size before the 

 exclusion of the young, and are exceetUngly numerous. The 

 young ones, when hatched, are extremely soft and small, and en- 

 tirely resemble their parent, beneath the abdomen of which they 

 shelter themselves for several days. The flesh of this animal is 

 much rehshed. It has been remarked that those which are 

 caught in clear and running streams are of a better taste than 

 those found in stagnant waters and in lakes. They are caught 

 by sinking a net, or spiny faggots, in the middle of which a piece 

 of putrid meat is placed. We well remember the delight with 

 which, in our schoolboy days, we could escape the trammels of 

 Bonnycastle and Virgil, and go groping, with our shirt-sleeves 

 tucked up, in the holes in brooks where the cray-fish were met 

 with, and can therefore speak from experience of the shai-pness of 

 the bite which they can inflict with their claws. The tops of their 

 claws were, in bygone times, employed in medicine, being con- 

 sidered as a valuable absorbent when pounded. Their place is 

 now supplied in om- pharmacopoeias by the carbonate of magnesia. 



The family PalcBmomda^ {Salicoques or Carides Latreille) 



