82 BRITISH PARASITIC COPEPODA. 



Antennules small. Antennae armed with strong 

 terminal hooks. Mandibles similar to those of 

 Lepeophtheirus but the end joint somewhat stouter and 

 more distinctly toothed. Second maxillae with the 

 endopodite slightly bifurcate. Second maxillipeds 

 tolerably elongated, not very robust and provided 

 with rather weak terminal claws. Sternal fork 

 small, with the rami simple, short, and slightly 

 divergent. The four pairs of thoracic legs all 

 biramose ; the first pair with both rami two -jointed, 

 but the rami of the other three pairs composed of 

 three joints ; the basal joint of the fourth pair short 

 and tolerably expanded, the rami also short and of 

 nearly equal length, the inner being rather the shorter, 

 both rami with the inner margins fringed with 

 tolerably long plumose setae. Fifth pair nearly 

 obsolete. Length about 10 mm. 



Male. Carapace orbicular and equal to about half 

 the entire length. Genital segment small, ovate, 

 somewhat longer but not much wider than the fret- 

 thoracic segment. Abdomen biarticulate, narrow, and 

 about as long as the genital segment; proximal joint 

 rather shorter than the end one. Length about 4*5 mm. 



Habitat. Parasitic on skates, rays, dogfishes, &c. 

 Belfast (W. Thompson). Polperro, Cornwall (A. M. 

 Norman). Plymouth (Bassett- Smith). Irish Sea 

 (A. Scott). Firths of Forth and Clyde and at Aber- 

 deen (T. Scott). 



Not very rare. The distribution of Trebius caudatus 

 appears to be somewhat limited; it is mentioned by C. B. 

 Wilson in his 'North American parasitic Copepods,' but the 

 specimens, he states, were collected off the coast of Shetland. 



Genus 11. ELYTROPHORA Gerstaecker, 1853. 



Female. Carapace rounded, frontal plates distinct 

 but without lunulaa. First three thoracic segments 

 fused with the head ; fourth segment with two dorsal 

 plates. Genital segment lobed posteriorly. Abdomen 



