174 CLASS CRUSTACEA. 



bodies, such as the valves of shells, of alcyones, with which 

 it covers itself: the tail has seven segments in both sexes. 



Some of them have, as well as the other brachyuri, the tail 

 folded underneath ; their feet are terminated by a sharp hook, 

 and are not adapted for swimming. 



In this division the testa is almost square, and terminated 

 anteriorly by an advanced and denticulated point, or it is 

 subovoid, or truncated in front. 



HoMOLA, Leach, 



Have the eyes supported by long pedicles, very much ap- 

 proximated at their base, and inserted below the middle of 

 the front ; the two posterior feet alone are raised ; the claws 

 are larger in the males than in the females. 



The head is very spiny, with an advanced and denticulated 

 projection at the middle of the forehead. The upper jaw-feet 

 are elongated and projecting. {Homola Spinifrons, Leach.) 



DORIPPE, Fah., 



Have the eyes very much apart, and situated at the lateral 

 and anterior angles of the testa, the four posterior feet raised; 

 the claws short in both sexes ; the testa ovoid, broadly trun- 

 cated, without any projection, in the form of a bill, and 

 flatted. 



As M. Desmarest has observed, we see on each side above 

 the origin of the claws, an oblique cleft, cut longitudinally by 

 a diaphragm, ciliated, like it, upon its edges, communicating 

 with the gills, and serving as an issue for the water. [Dorippe 

 lanata, Cancer lanatus, Linn., Desmarest, &c.) 



In the others, the testa is sometimes almost orbicular or 

 globular ; sometimes arched in front, and contracted pos- 



