116 BRITISH PARASITIC COPEPODA. 



lateral margins slightly convex. Abdomen and caudal 

 rami very small. 



Antennules short, moderately stout, and consisting 

 of about five joints, the first large and equal to nearly 

 all the other joints combined, and its lower distal angle 

 produced downwards in the form of a strong hook ; 

 the three end joints subequal and shorter than the 

 preceding one ; several short, dagger-like spines 

 springing from the upper margin of the various 

 joints. Antennae about as long as the antennules, 

 two-jointed and armed with stout terminal claws; a 

 small process in the form of a knob occurs at the base 

 of each antenna. Mandibles and maxillse small and 

 simple in structure. Maxillipecls moderately slender, 

 composed of two (or three) joints, and with the 

 extremities uncinate. Thoracic legs two pairs, both 

 biramose and somewhat similar in structure ; the basio- 

 podite consisting of two moderately stout joints and 

 both rami also two-jointed, the inner ramus in both 

 pairs being rather more robust than the outer one; the 

 proximal joint of the outer ramus the largest and 

 bearing a small spine on its outer distal angle, the 

 joints of the inner ramus also unequal but the proximal 

 one the smaller. Caudal rami short. Length about 

 1 mm. Egg-strings fully as long as the animal, and 

 with proportionately few but rather large ova. Colour 

 similar to that of the gills of the host. 



The male of this species has not yet been observed. 

 Habitat. Parasitic on the gills of the striped Avrasse, 

 Labrus mixtus Linn., and the ballan wrasse, Labr/i* 

 bergylta Ascan. (Labrus maculatus Bloch). Firth of 

 Clyde ( T. Scott). Irish Sea (A. Scott). Professor P. J. 

 van Beneden states that Hatschekia labracis is abundant 

 on both of the species of fish mentioned above. 



This Hatschekia, though distinct enough, is very small ami 

 easily overlooked, but as the egg-strings are of a somewhat 

 lighter colour than the gills of the fish, and tolerably 

 elongated, they help to reveal the presence of the parasite. 



