REPORT ON THE CRUSTACEA MACRl'KA. 42] 



the carapace ; the third joint of the peduncle is subequal in length to the second, and 

 the two together are equal in length to the first. 



" The second pair of antennse with the scaphocerite sublinear, and six times as lung as 

 broad ; the last joint of the peduncle is linear, and three times as long as broad. 



" Sixth somite of the pleon scarcely a sixth part of the length of the entire animal, but 

 fully as long as the first and second somites together, scarcely shorter than the fourth 

 and fifth somites together, more than twice as long as broad, and scarcely one-third 

 longer than the telson ; it is armed with a sharp point on the posterior dorsal margin. 



" Pleopoda very slender, the anterior pair nearly subsetiform. 



" Rhipidura having the external branch armed with a sharp point, about one-fourth 

 distant from the apex. 



" Habitat. — Greenland " (Kroyer). 



Observations. — No specimen in the Challenger collection corresponds precisely with 

 the description and figure given by Kroyer, but there are three forms that somewhat 

 closely resemble it. Two were taken in the North Pacific, and one in the North Atlantic. 



The one described as Sergestes prtecollus was taken north of the Sandwich Islands. 

 It corresponds most closely, but differs in having the rostrum reduced to a mere angle, 

 and the ophthalmopoda slightly compressed behind the ophthalmus, the' stalk gradually 

 decreasing to the articulation ; and carries a very long and outwardly directed tooth on 

 the outer margin of the outer plates of the rhipidura, in the position mentioned by Kroyer. 



Sergestes longieottus, n. sp. (PI. LXXVII. fig. 1). 



Rostrum reduced to a small point on the frontal margin. Carapace considerably 

 more than one-third the lenoth of the animal, little less than one-half, exclusive of the 

 telson. 



Pleon dorsally smooth ; the four anterior somites subequal, the fifth a little longer 

 than the preceding, all with the mferodateral angles rounded off; sixth about twice as 

 long as the fifth, posteriorly furnished with a small dorsal tooth. 



Telson about half the length of the sixth somite. 



Uphthalmopod one-fifth as long as the carapace, and reaching as far as the extremity 

 of the first joint of the peduncle of the first pair of antenna?. Ophthalmus a little broader 

 than the stalk, which gradually narrows to the base. 



First pair of antennse with the first joint as long as the ophthalmopod, the second 

 joint about half the length of the first, and the third subequal to, or a trifle longer than, 

 the second ; flagellum wanting, secondary branch slender and feeble, and as long as 

 the third joint. 



Second pair of antenna? with the terminal joint of the peduncle cylindrical and 



