DECAPODA. 309 



countries. Their habits are a constant source of interest to travellers, 

 but by abstracting from their accounts all improbable and doubtful facts, 

 their history will be as follows. The greater portion of their life is passed 

 on land, where they secrete themselves in holes, from which they never 

 issue but at night. Some inhabit cerf.eteries. Once in the year they col- 

 lect in immense bands and pursue a direct course to the sea, heedless of all 

 obstacles; after depositing- their ova, they return much enfeebled. It is 

 said that they seal up the mouth of their burrow during the time they are 

 casting their shell. 



FAMILY II. 



MACROURA(l). 



In the Decapodu Macroura, the end of the tail is provided with 

 appendages which most frequently form a fin on each side; the tail 

 itself is at least as long as the body, extended, exposed and simply 

 curved towards its posterior extremity. Its under surface usually 

 presents in both sexes five pairs of false feet, each terminated by 

 two lamina?, or as many filaments. This tail is always composed 

 of seven distinct segments. The branchiae are formed of vesicular, 

 bearded and hairy pyramids, arranged in several of them, either in 

 two rows, or in separate fasciculi. The antennae are generally 

 elongated and salient. The ocular pedicles are usually short. 

 The external foot-jaws are mostly narrow and elongated, resembling 

 palpi, and do not wholly cover the other parts of the mouth. The 

 shell is narrower and more elongated than that of the Brachyura, 

 and usually terminates by a point in the middle of the front. 



With De Geer and Gronovius, we will arrange them in a single genus, 

 that of 



ASTACUS, 



Which we divide in the following manner. Some, by the proportions, 

 figure, and uses of their feet, of which the first, or at least the second pair, 

 are in the form of claws, and by the subcaudal situations of their ova, evi- 

 dently approach the preceding Crustacea, and approximate still more 

 closely to those commonly known by the names of Crawfish, Lobster, and 

 Shrimp. 



The feet of the others are very slender, and are furnished with an exte- 



(1) Long-tailed. 



