PORTUNUS. 89 



of Crab presumed by Pennant and by Leach to be the one 

 in question, would point to the same supposed office. That 

 they do perform such an office in no very limited degree, 

 may be concluded from the localities in which they abound, 

 and the numbers in which they are found congregated. 

 In the refuse of the prawn and lobster pots, where they 

 resort for the purpose of feeding on the often half-putrid 

 garbage which is placed there as bait, and amongst the 

 mass of miscellaneous filth sometimes brought up by the 

 dredge, hundreds of these cleansers are frequently taken. 



The genus Portunus as established by Fabricius, was 

 much more extensive than at present, including as it did 

 the whole of the swimming Crabs belonging to this divi- 

 sion ; in fact, the whole family of Portunidte, as far as 

 they were then known, with the exception of Carcinus, 

 which forms one of the links by which the family of Cance- 

 rida are united with the present group. 



