BRITISH STALK-EYED CRUSTACEA. 103 



sharply pointed. The forceps are armed with two serrated 

 ridges, and the spine on the wrist is of a different shape from that 

 of P. marmoreus, not being so acute. The swimming blades are 

 also much more rounded in form than those of the last species. 



Professor Bell says that — " The appearance of this crab is 

 extremely rare on our coasts "; though he cites several instances 

 of its by no means isolated occurrence. It is, however, no doubt 

 local, but existing in enormous quantities where the surrounding 

 circumstances are favourable to its development ; for instance, in 

 August, 1880, we obtained a large and fine series from a sand- 

 bank near the Nore light-ship, in the estuarj' of the Thames, by 

 means of a trawl, although none were to be found on adjacent 

 spots possessing apparently equal advantages. Portunus holsatus 

 has also been recorded from the Firth of Forth, Cornwall, and 

 the Bays of Belfast and Dublin ; St. Andrews (not uncommon) ; 

 Shetland (frequent) ; Berwick (specimens small) ; Hebrides ; 

 Sunderland coast, " plentiful in rock-pools." 



Portunus corrugatus, Leach. 



This remarkably well-defined species may be at once deter- 

 mined by the corrugated formation of the carapace, from which it 

 derives its name. This appearance is caused by very finely 

 serrated ridges, which cover the carapace transversely, and is 

 also developed upon the limbs of the animal. The anterior 

 portion of the carapace is armed with five teeth on each side of 

 the orbits, and the space between the orbits is occupied by three 

 blunted prominences scarcely attaining to the dignity of teeth. 

 The carapace is narrowed abruptly towards the posterior margin. 



The anterior pair of legs are frequently unequal in size, but 

 more uniform in shape than those of the other members of the 

 genus. The spine on the wrist is long and sharp, and the chelae 

 evenly serrated. The swimming blade of the posterior legs in 

 this species is small and narrowed towards the apex; the terminal 

 joints of the other legs are acutely pointed. 



The colour is of a rich reddish brown, often marked with 

 patches of darker red or brown. According to Bell, Portunus 

 corrugatus " must be considered as one of the rarer species of the 

 genus," and his records of its capture certainly tend to prove that 

 it was by no means commonly known at that period. The 

 localities named by him are the Island of Skye, Plymouth Sound, 



