ORDER DECAPODA. 173 



Calappa, Fah.y 



Have the testa very gibbous, the forceps triangular, very 

 much compressed, denticulated above, like a ridge or crest, 

 and covering perpendicularly the front of the body, when the 

 feet are contracted. The third articulation of the external 

 jaw-feet is terminated like a hook ; the superior extremity of 

 the buccal cavity is narrowed, and divided longitudinally into 

 two lodges by a partition. 



Some, and the most numerous, have the two posterior and 

 lateral dilatations of the testa incised, and denticulated. {Can- 

 cer granulatus, Linn., Calappa granulata, Fab.) 



Others, such as Calappa fornicata, Fab., have the edges 

 of the dilatations of the testa entire. 



^THRA, Leach, 



Differ from calappa, by their very flatted testa, their forceps 

 not raised perpendicularly, nor shading the front of the body, 

 and the almost square form of the third articulation of the ex- 

 ternal jaw-feet. 



Sometimes, {JEthra depressa, Lam.) the testa is in a trans- 

 verse oval ; sometimes, {Parthenope fornicata, Fab.) in the 

 form of a short triangle, very broad, dilated, and rounded 

 laterally. The claws are but little elongated, and tolerably 

 thick ; but sometimes they are longer, angular, and remind us, 

 as does also the form of the testa, of the parthenopes. These 

 last species might form a subgenus proper. 



Finally, a seventh and last division, Notopoda, is formed 

 ofbrachyuri, whose last four, or last two feet, are inserted 

 above the level of the others, or seem to be dorsal and turn 

 upwards. In those in which they are terminated by a sharp 

 hook, the animal usually employs it to retain divers marine 



