34 BRITISH PARASITIC COPEPODA. 



two- or three- jointed, more or less prehensile, and 

 usually armed with terminal claws. Mandibles small. 

 Maxillae rudimentary. First maxillipeds small and of 

 a simple structure. Second maxillipeds well developed 

 and provided with strong terminal claws. First four 

 pairs of thoracic legs biramose ; both rami of the first 

 three pairs composed of three articulations, but in the 

 fourth pair, while the inner ramus is three-jointed, as 

 in the other three pairs, the outer may consist either 

 of three joints or only of two. Fifth pair small, one- 

 branched, uniarticulate or rudimentary. Egg-strings 

 two. 



Genus 1. ERGASILUS Xoflmann, 1832. 



Somewhat like Cyclops in general appearance. 

 Cephalothorax elongated, segments five, the first 

 segment large. 



Antennules composed of five or six joints. Antenna? 

 elongated and composed of three joints, terminal claws 

 large, and forming powerful grasping organs. First 

 four pairs of thoracic legs biramose ; both rami of the 

 first three pairs three-jointed ; fourth pair with the 

 inner ramus three- and the outer two-jointed. Fifth 

 pair small or rudimentary. Egg-strings two. 



1. Ergasilus nanus P. J. van Beneden. 



(Plate I, fig. 1; Plate 11, figs. 1-5; Plate XLVIII, 



fig. 17.) 



1870. Eryasilns nanusP. J. van Beneden. (16) Les Poissons des cotes 

 de Belgique, leurs parasites et leurs comniensaux, p. 27, pi. i, fit;-. <; 

 (recorded and figured but not described in this work). 



1901. Ergasilus tutnus T. Scott. (113) p. 122, pi. vii, figs. 1-8. 



Female. Body somewhat expanded anteriorly, pos- 

 terior extremity attenuated. Cephalic segment large, 

 and if viewed from above, somewhat pear-shaped in out- 

 line ; the widest part, which is near the anterior end of 

 the segment, equal to fully half its length, and a shallow 



