AMPHIPODA. 
19 
Antennae subequal, as in P. ( Probolium ) gregarium (G. 0. Sars) ; no appendage. 
Mouth organs as in P. gregarium. 
Maxillipeds with the inner lobes very small and separate, the outer (masticatory) 
represented by a dilation and distal prolongation of the inner margin of the joint. 
First gnathopods : Wrist subequal in length to, but wider than, the hand ; the hind 
margins of both convex and setose, otherwise as in P. gregarium. 
Second gnathopods : Side-plates with the front and lower margins forming a 
continuous curve, hind margins almost straight. First joint as long as the next four ; 
third joint rather acutely produced behind ; wrist with a rounded process ; margins of 
the hand subparallel; hind margin subequal to the palm, which is defined by a small 
tooth and two spines. 
First and second, perseopods resembling those of P. gregarium, the second being 
stouter and more spinous than the first, but the side-plates are more rounded in front. 
Third perseopods : The posterior lobe of the side-plate is suboval and considerably 
produced downwards. The concave hind margin of the narrow first joint is prolonged 
almost to the end of the second, terminating in a divided lobe. 
Remaining perseopods as in P. gregarium. 
The second uropods are subequal in extent to the third, the peduncle subequal to 
the inner ramus, which is almost twice as long as the outer ; this has two spines, the 
inner and peduncle several. 
Third uropods : The peduncle is shorter than the ramus and has five spines; the 
first joint of the ramus is subequal to the second and has three spines. 
The telson reaches the end of the peduncle of the third uropods and has three 
spines on each margin. 
Length, 3 • 5 mm. 
The male is considerably larger than the female. Upper antennse reaching to the 
middle of the flagellum of the lower. Peduncle of the lower twice as wide as that of 
the upper, the second joint as long as the flagellum, which is 12-jointed, the first 
joint as long as the next three. 
Fit 1 st gnathopods : Wrist considerably longer and but slightly wider than the 
hand. 
Second gnathopods : Side-plates rounded in front, hind margin concave, the 
posterior part of the lower margin irregularly serrate. First joint rather longer than 
the next three; second with a prominence on the front; wrist produced behind. 
Hand as long as the three preceding joints, subtriangular, hind margin shorter than 
the front and ending in a sharp tooth ; palm deeply excavate, with a central tooth and 
a denticulate ridge near the base of the dactylus. 
In a younger male the palm is less deeply excavate, the central tooth wider, 
blunter, and denticulate, and the ridge as wide as the excavation. 
Associated with this species were two or three females characterized by the concave 
lower margins of the side-plates of the second perseopods. 
