Dr. T. Scott on British Copepoda. 462 



Type species Leptaslacus macronyx, T. Scott. Described 

 under the name of" Tetragoniceps macronyx" in the 'Tenth 

 Annual Report of the Fishery Board for Scotland/ pt. iii. 

 p. 253, pi. x. figs. 19-28 (1892). Ltptastacus macronyx was 

 provisionally ascribed to the genus Tetragoniceps, G. S. Brady, 

 because of its slender form and because in some structural 

 details it had a resemblance to that genus. The occurrence 

 of specimens from other localities has enabled me to study 

 more carefully the peculiarities of this form, and I now think 

 that though it is closely allied to Tetragoniceps, G. S. Brady, 

 its position in that genus can scarcely be maintained. The 

 structure of the anterior antennae, the rudimentary character 

 of the outer ramus of the posterior antennae, the structure of 

 the mandible-palp, of the first maxillipeds, and of the fifth 

 pair of thoracic feet all differ more or less from the typical 

 Tetragoniceps. 



This species seems to have a fairly wide distribution, as I 

 have observed it in the estuary both of the Forth and Clyde. 



Genus D'Arcythompsonia, T. Scott, nov. 



Animal closely resembling Cylindropsyllus, G. S. Brady, in 

 its general form. Body elongated, narrow, cylindrical, with 

 no distinct separation between the thorax and abdomen. 



Anterior antennas in the female short, eight-jointed, the 

 four proximal joints being tolerably robust, while the last 

 four are distinctly more slender than the others. Posterior 

 antennas three-jointed ; outer ramus uniarticulated and rudi- 

 mentary. Mandibles small, narrow towards the distal end, 

 armed with a few blunt-pointed apical teeth ; the mandible- 

 palp small and uniarticulate. Maxillas broadly lamellifonn 

 and with the truncated apex furnished with several tooth-like 

 spines; palp small and two-jointed. Second maxillipeds 

 robust, two-jointed, and terminating in a strong bifid claw. 

 The first four pairs of thoracic legs have the outer branches 

 three- and the inner two-jointed. In the first pair the inner 

 branches are nearly as long as the outer and the joints are 

 suuequal in length, but in the other three pairs the inner 

 branches are considerably shorter than the outer branches. 

 The fifth pair are very small, one-jointed, and lamelliform. 

 The abdomen is composed of five segments. 



The male is similar to the female in its general form, but 

 the anterior antennfe appear to be only six-jointed, the 

 structure of the last four joints being considerably modified. 

 The second pair of thoracic legs differ from those of the 

 female in the presence of a tolerably long, stout, spine-like 



