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the tail, which is emarginate. The body is elongate-ovate, 

 and convex, the eyes large and nearly meeting on the 

 crown ; the upper pair of antennae are not longer than the 

 head, with aflagellum composed of about twelve articula- 

 tions, the two basal joints very broad (the second obliquely 

 emarginate), with the nagellum affixed on its hinder angle. 

 The coxae of the legs attached to the anterior segments 

 of the pereion are sub quadrate and marked with straight 

 elevated ridges; these are represented in our upper right- 

 hand figure as seen on the underside of the body, show- 

 ing the base of the three fore legs on the left side. 



The branchial plates on the underside of the body (as 

 represented in our lower left-hand figure) scarcely ex- 

 tend beyond the middle of the terminal segment ; they 

 are all of nearly equal size, the upper or outer pair not 

 covering the whole or even the following pair. The 

 lateral appendages also, when folded up, scarcely extend 

 beyond the lateral margins of the terminal segment, the 

 truncated extremity of each inner division uniting and 

 leaving a triangular space uncovered at the extremity of 

 the tail ; the outer division of these lateral appendages is 

 considerably smaller than the inner, and elongate- ovate 

 in form, pointed at the tip, with the outer edge armed 

 with spines arranged in transverse rows. 



The typical specimen of this species described by 

 Leach was contained in Sowerby's collection from Scot- 

 land, and Mr. Gregor has sent it to us from the Moray 

 Frith, and there are others now in the British Museum 

 from Belfast, presented by Colonel Portlock. 



The late Mr. "W. Thompson, of Belfast, also obtained 

 it from Belfast Market, where it was found among Car- 

 rickfergus oysters, at the end of March, 1839, and also 

 from a cod-fish brought to the same market in February, 

 1841. 



