840 MYSID.E. 



sides ; lateral plates somewhat subulate, ciliated on each 

 side. 



Mr. J. Y. Thompson appears to have been the first to 

 distinguish this species of Mysis, to which he gave the 

 name vulgaris, probably from its being the most common 

 species in the locality where he found it. It is, however, 

 more rare on oiir coasts, and probably, as it had escaped 

 detection, also on those of other countries. The specific 

 name which he assigned to it is always one of doubtful 

 propriety, and I would fain have assigned to it that of the 

 distinguished naturahst by whom it was first discovered 

 and described, but from a disinclination ever to change a 

 specific name excepting under urgent circumstances. 



It appears to be a local species, and as far as we are 

 at present able to say, is principally found on the Irish 

 coast; "abounding in the Lee," says Mr. J. V. Thomp- 

 son, " even up to Oork," and I have specimens collected 

 by Mr. W. Thompson in Belfast Lough. From the former 

 species it may be at once distinguished by several promi- 

 nent characters, particularly the longer antennal scale, and 

 the simple acute apex of the middle caudal lamina. Its 

 colour is pale, translucent grey. 



The following is Mr. Vaughan Thompson's account of 

 its habits. " They swim with the body in a horizontal 

 position, and abound in the Lee, even up to Cork, from 

 the early part of spring to the approach of winter ; during 

 the still period of the tide at low water, they repose upon 

 the mud and stones at the bottom of the river, and as the 

 tide rises, may be observed forming a wide belt, just within 

 its margin, the youngest swimming nearest to the shore, 

 the oldest further out, and in deeper water : they appear 

 to be mostly females, the males being few in proportion. 

 This species contributes towards the food of various young 



