DUBLIN NATUEAL HI8T0EY SOCIBTY. i 



brought up in the dredge ; for when the speed waa slackened, we got 

 Pectunculus, but no crabs ; and this I suppose was the literal feet. The 

 depth of water was about twenty-two fathom, and the bottom a^hard 

 yellow sand. 



When I asked the men whether M*Calla had ever dredged there, they 

 said he never had ; and when I inquired where he could have obtained 

 the carapace, they at once replied at Gurteen strand, about two miles 

 from the spot, that being the only spot where dibris was thrown up. 

 They also mentioned that the dredge he had was small, and would not 

 sink hero, as the current was so strong, and this I found to be the case. 

 It is in vain to go with the current or against it — in the first case the 

 net is reversed and goes before the dredge ; in the latter case the dredge 

 floats, and, should it reach the bottom, it hops, and never lies permanently 

 on the ground ; the current must be crossed, and this requires a good 

 vessel, a heavy dredge, and good men to work it, and these M'Calla never 

 had, owing to the rather heavy expenses attending them, so that, 

 from this account, it would appear that the animid lived and died 

 on this bank, and was carried by the current and thrown on Gur- 

 teen Strand, and there found in its mutilated state by M'Calla, who had 

 thence determined the species. I have now given an account of the 

 capture of the crab, and its locality. It appears to me that a current 

 is its domicile — it is hever found in the sluggish waters of either bays, 

 where Portunus corrugatua is found abundantly. It is a very active crab, 

 and it behoves it to be so, as the current which carries its prey runs at the 

 rate of seven or eight nules an hour. We have seen that it has activity 

 enough to avoid the dredge when the vessel was not under very rapid way. 



I alluded to the difficulty of preserving the colours of the Crus- 

 tacea. I am happy to say that that is now removed, and henceforth 

 this class of animals will grace our museums in aU their varied and 

 beautiful colours. I am indebted to Colonel We^g for being in a posi- 

 tion to show the result of his scientific applications. Immediately on 

 getting those specimens, I packed them up in a small box, filling up 

 the remaining space with fresh chopped sea- weed {Fucus vesiculosus), 

 and forwarded them to him by mail. His success was far beyond my 

 most sanguine expectation. The specimens are in appearance this mo- 

 ment as fresh as when taken, nearly six months since. 



Before I close, I may be permitted, in the words of Bell, to say — "that 

 the portion of the crab denominated the carapace is the outer shell or 

 the large enveloping buckler which covers the entire of the thorax ; and 

 even the abdomen itself is folded underneath it, so that the whole animal 

 is hidden by it. This remarkable buckler, covering as it does the whole 

 of the viscera, is found to be more or less divided distinctly into regions, 

 which are indicated by elevations separated from each other by grooves, 

 and to these regions have been given names derived from the different 

 organs which are immediately covered by them." 



In the species Portunm marmoreu8 the abdomeain the male is five- 

 jointed ; in the female, seven-jointed. 



