MONOPHTHALMA. 287 



coalesce dorsally and centrally ; they are reticulated and 

 extend obliquely backwards, leaving a small point pro- 

 jecting anteriorly between the base of the upper antennae 

 and a small central triangular space behind. The inferior 

 antennae are separated at the base by a small oblong 

 concave plate or labrum. The seven segments of the 

 body are nearly equal in size, marked with a faint line 

 across the middle ; their sides are furnished with strong 

 coxae pointed posteriorly, and with two slight ridges down 

 the middle. The first three pairs of legs are directed 

 forwards ; they are robust, and furnished with strong 

 curved claw-like fingers ; the four posterior pairs of 

 legs are longer and much more slender, with the joints 

 nearly equal and spinose, terminated by curved fingers. 

 The tail is formed of six segments, of which the five 

 first are short and equal, and the terminal one broad, 

 oblong, roughish, depressed, with a strong keel down the 

 centre ending in a short mucro ; the margins of these 

 segments are minutely spinose ; on each side of the ter- 

 minal segment is a pair of foliaceous plates articulated 

 to a movable, acutely pointed, somewhat triangular pro- 

 cess ; the inner plate is wedge-shaped and the outer one 

 oblong ; both are densely ciliated round the edge. 



Dr. Johnston, whose detailed description is slightly 

 abridged above, adds that this species swims with rapidity 

 by the aid of its " caudal fins," and when it comes in 

 contact with a solid body it clasps against it and adheres 

 tenaciously. His specimens were taken adhering to large 

 cod-fish, of which it is probable they are the " pedicular 

 parasites ;" but, unlike some of their race, they appear to 

 be very rare, at least in Berwick Bay, as he could only 

 procure three individuals, and the fishermen had never 

 observed them before. 



Dr. Johnston also described and figured as a variety of 



