neto Parasitic Copepods on Fish. 81 



Female. — The cephahthorax being folded up as a mussel 

 is deeply notched in front and behind, the length of each 

 valve is much greater than the breadth, and equals about 

 two fifths of the total length ; it has a rounded, somewhat 

 lobed border, and fringing the margin is a wide band of lineate 

 structure, which on higher magnification is seen to be due to 

 minute parallel canals, and no doubt assists in the holding 

 power of the valve ; on the dorsal surface the chitinous ribs 

 are seen as described by Heller. 



Frontal plate narrow, with a straight border, from the 

 outer and under side of which rises the antenor antenncB ; 

 these are small, two-jointed, the basal being longer than the 

 second, having on its front border about ten ciliated sette ; 

 the second joint is rod-shaped, terminating in a few fine 

 bristles. 



Posterior antennce placed some distance back from the 

 frontal border ; they are very long and strong, the claw-like 

 ends projecting well in front of the anterior border; each is 

 composed of three joints — the basal is short, thick, and mus- 

 cular, carrying a small sharp-pointed spur directed backwards, 

 as in many of the " Caligid^e " ; the second joint is short and 

 thick, bearing the long terminal claw-joint on a firm articu- 

 lation ; it is widely curved, sharp-pointed, and has on its 

 concave border one third from the point a secondary sharp 

 hook, rather less long, but not articulate. 



Rostrum of moderate size, three times as long as broad, 

 tapering to the point. 



First maxiUiped very small, two-jointed, with a sharp- 

 pointed palp near its base. 



Second maxiUiped very long, two jointed, the first being 

 oval and muscular, the second slender, curved, chitinous, 

 terminating in a short sickle-shaped point, with a minute 

 tooth at its base. 



Furcida very small, with a short dilated base, bearing 

 straight, pointed, slightly divergent branches ; the distance 

 between the points equals the length of the branch. 



First ferceopod three-jointed, the basal short and thick, 

 with a small lobe from the inferior border ; the second joint 

 is about twice as long, the third is short, bearing on the 

 under border three long plumose hairs ; at the extremity are 

 seen three long straight bristles, the upper being the longest, 

 equalling the whole length of the limb; at the angle is a 

 very short bristle. 



Second percEopod oi the usual form ; third as in " Caligus " ; 

 the two branches are here placed close together and are very 



