570 Dr. T. Scott on British Copepoda. 



secondary joint, so tliat there is a comparatively wide space 

 between the two pairs. The secondary joint, which is 

 lanielliform and with nearly parallel sides, is about one and a 

 half times longer than broad, the width slightly increasing 

 toward the distal end ; it is provided with five seta3, one on 

 the outer margin and four round the distal extremity ; the 

 marginal seta, which springs from a notch on the outer edge, 

 is stout and spiniform ; the outermost and innermost of the 

 four apical setse are of moderate length, but the other two 

 are short. 



The furcal joints^ which are rather shorter than the last 

 abdominal segment, are comparatively widely apart and also 

 somewhat divergent. 



Thompsonula, T. Scott, gen. nov. 



My friend the late Mr. I. C. Thompson, of Liverpool, 



wbose interesting discoveries have added so much to our 

 knowledge of the Copepod fauna of the British Islands, 

 described in 1899, under the name of Jonesiella hycence^ a 

 somewhat curious form that had recently been observed in 

 some collections from Port Erin Bay, Isle of Man. This 

 form was also subsequently obtained in the Firth of Forth 

 and at some other places around our shores, and its distribu- 

 tion as now known is fairly extensive. 



Although this form was included in the genus Jonesiella^ 

 G. S. Brady, it differs from the typical members of that 

 genus in one or two important particulars, and especially in 

 the structure of the first pair of thoracic feet. In the generic 

 definition given by Professor Brady the inner branches of the 

 first pair are described as " two-jointed, and bearing long- 

 terminal seta?, but no claws " ; in Jonesiella hyance, on the 

 other hand, the inner branches are distinctly three-jointed. 

 In my remarks on this species in the ' Eleventh Annual 

 Report of the Fishery Board for Scotland,' part iii. p. 203 

 (1893), it is stated that " these differences may render it 

 necessary to modify the generic description or to remove 

 Jonesiella hymnoi to another genus •'"' *. I now propose to 

 adopt the latter of these suggestions, and have named this 

 new genus after my late friend. 



Definition of the genus Thompsonula. — Somewhat similar 



* It is interesting to note that Mr. I. C. Thompson also realized the 

 difficulty referred to here, but was inclined " to slightly modify an existing 

 genus rather than make a new one,"' 



