470 



BULLETIN OF THE BUREAU OF FISHERIES. 



rounded lobe, the distal margin forming a palm against which the finger closes; a deep notch between 

 this lobe and base of finger; second gnathopods of male with propodus very large and stout; palm very 

 oblique, convex, and notched a short distance within the posterior angle, which is a little produced; 

 " the margin, when viewed laterally, shows a broad lobe next the base of the dactylus and two small, 

 rounded lobes near the posterior angle, the tip (if the finger resting between the small lobes." In the 

 female neither carpus nor propodus is furnished with a lobe, although the posterior margin of the 

 former is somewhat produced below the middle; second gnathopods of female with propodus 

 oblong, rounded below, and furnished on the anterior margin with a minute dactyl which does not 

 reach the lower end; merus and carpus in posterior peneopods of adult male swollen; rami of first 



a.al. 



ury 



i hiii, stia affUU. tin- antenna and uropode are drawn to a different scale from the other parts, and the gnathopods of 

 the male are ilrau 11 to a larger scale than those of the female. Specimens from Woods Hole. 



U 



uropods markedly shorter than peduncle; those of second uropods subequal to peduncle; ramus of 

 posterior uropods several times narrower than the thick peduncle but nearly as long; telson narrowly 

 rounded behind or more or less pointed, spinulous. 



Length, 1 cm. 



General color, olive brown; antennae red or reddish brown; legs, coxal plates, and after portions 

 of the body of a bluish color. 



Bay of Fundy to New Jersey. 



This species is exceedingly abundant under the masses of seaweed near the shore. It is seldom 

 found so far up on the beach as Talorcfteslia, and is much more active during the daytime. Its specific 

 name is very appropriate, as it hops with the greatest rapidity and, in relation to its size, to a remarkable 

 distance. It is by far the most active of all the sand fleas of the region. When masses of seaweed 

 are upturned the air sometimes fairly swarms with these amphipods. Like TcUorchestia this species 

 lives mainly upon seaweed, although it seems In be quite omnivorous and will not disdain animal 

 food. It is seldom found under masses of drift thai are not damp, or if so it is buried some distance 

 in the sand. 0. agilis wDl bear immersion fur over a week in sea water, as I have determined by 

 experiment, and is able to swim, when necessary, as if to the manner born. Occasionally 1 have 

 found specimens on piles at a considerable distance from the shore — fortunate survivors, doubtless, i>f 

 forms overtaken by the waves and carried out to sea. hike Talorchestia longicornis this species is 

 strongly attracted to the light, although under certain conditions it may become negatively phototaetic. 



