132 BRITISH PARASITIC C0PEP0DA. 



setae — one at the apex and two on the lower half of 

 the outer margin. Length about 3 mm. 



Male. — The male is smaller than the female, the 

 body is more slender, and the abdomen is about as long 

 as the cephalothorax. Antennules tolerably stout and 

 composed of about seven articulations ; the first and 

 second joints are short but considerably dilated, the 

 second is provided with a stout and strongly curved 

 spine which springs from the upper distal angle ; the 

 remaining joints are all nearly of equal width and 

 much narrower than the basal joints, the third joint is 

 about as long as broad, the fourth and fifth are very 

 short, the sixth is rather longer than the fourth and 

 fifth combined, while the end joint is nearly three 

 times the length of the sixth ; the third and fifth 

 joints are each furnished with a stout and moderately 

 long straight spine, and a shorter spine also occurs on 

 the distal end of the sixth joint, while the last joint 

 is armed with a strong terminal hook and a slender 

 sensory filament. Antennae and mouth-appendages 

 like those of the female except that the second maxilli- 

 peds are not chelate but provided with a simple 

 terminal claw. The first four pairs of thoracic legs 

 have both rami three-jointed, but the articulation 

 between the second and third joints of the outer ramus 

 of the first pair is not clearly defined ; the inner ramus 

 of the second pair is provided with a tolerably 

 elongated and slightly curved spine which springs 

 from the inner distal angle of the first joint ; the outer 

 ramus of the second pair is normal in structure. Both 

 rami of the third pair are moderately slender and 

 setiferous. Fifth pair somewhat similar to those 

 of the female. Caudal rami narrow, each with two 

 apical and one marginal spiniform setae. Length about 

 2 mm. Colour similar to that of the gills of the fish. 

 Egg-strings moderately slender and elongated. 



Habitat. — Parasitic on the gills of the starry ray, 

 Baia radiata Don. The fishes on which this parasite 

 was obtained were captured east of the Shetland 



