02^ ILYOPSYLLtJS COBIACEUS AND OIHEK CKUSXACEA, ETC. 429 



XVI. — On Ilyopsyllus coriaceus and other Crustacea taken at 

 Alnmonth, NorthumherlanA^ in 1899. By Geojige Stewakdsox 

 Bkadt, M.D., LL.D., D.Sc, F.R.S., C.M.Z.S. (Plates XI.— 

 XIII). 



The remarkable little Crustacean which, forms the principal 

 subject of rhis paper was first described from specimens taken 

 by the late Dr. David Robertson and myself in 1872. These 

 specimens were found in black peaty mud about the roots of 

 fuci near the head of Roundstone Bay, Ireland, and not far from 

 high water mark. The mud was collected for the sake of any 

 shells of Foraminifera and Ostracoda which it might contain, 

 and was simply bagged and dried for examination at home. 

 Copopoda of ordinary constitution would have been so shrivelled 

 by this treatment as to be practically useless and indeed almost 

 unrecognisable, but this species possesses an integument so 

 dense as to undergo comparatively little change in drying, 

 while its usually vivid red colour, which seems to withstand not 

 only desiccation but most chemical reagents, renders it easy of 

 detection amongst its native mud. Nevertheless I was unable 

 from the dried material to make out satisfactorily the more 

 minute details of its structure, and from that time up to the 

 autumn of the present year (1899) no further material has been 

 available. About ten years ago I found a single specimen 

 amongst a gathering of mud-loving brackish water species from 

 Lymington, Hants ; and I have had sent to me — I think by Dr. 

 Chevreux, though I have no written memoranda — two or three 

 specimens found in oyster-ooze from Arcachon, France. And 

 only this morning Dr. Norman writes to me as follows: — "I 

 have lately found Ilyopsyllus in a gathering made in 1874 in 

 Birtirbuy Bay ; and after all these years in spirits the brilliant 

 red colour remains." I am not aware that the species has been 

 seen by any other observer, except Mr. T. Scott, who has 

 taken a single specimen at the mouth of the River Alness on 

 the Cromarty Firth. 



