REPORT ON THE CRUSTACEA MACRTJRA. 403 



only feature that makes me hesitate to pronounce it to be a younger form of the latter 

 species, which it may be and probably is, only just escaping from the Mastigopus stage; 

 the second and third pairs of perciopoda are just assuming their chelate condition. The 

 animal from which our figure is taken is scarcely a mature one. 



Sergestes edwardsii, Kroyer (PL LXXIII. fig. 2). 



Sergestes edwardsii, Kroyer, Monograph. Fremstilling af Kraeb. Sergestes, pp. 30, Gl, Tab. iv. 



fig. 9 a-k. 



" Rostrum rudimentary, directed obliquely upwards. 



" Ophthalmopoda slender, shorter than the first joint of the peduncle of the first pair 

 of antennas. Ophthalmi not distinct from the pedicle, nearly as long as broad, and 

 nearly one-third of the length of the ophthalmopod. 



" First pair of antennae having the peduncle about one-fifth shorter than the carapace: 

 the third joint is rather shorter than the first and longer than the second. 



" The second pair of antennae has the terminal joint of the peduncle short, broad, sub- 

 ovate, and in length nearly equal to one-third of the scaphocerite. 



" Sixth somite of the pleon about one-sixth of the length of the animal, or as long 

 as the fourth and fifth somites together, or as the first and second united ; about twice 

 as long as broad, and scarcely one-third longer than the telson ; inferior margin sub- 

 angular. 



" Pleopoda robust. 



" Rhipidura having the outer ramus destitute of a tooth." 



Habitat.— North Atlantic, Aprd 1873. 



Pacific Ocean, surface, September 1875 ; 



Cape Verde Islands, April 26, 1876. 



Greenland (Kroyer). 



Length, 9 mm. (0-33 in.). 



Rostrum small, pointed, slightly elevated anteriorly. Carapace less than one-third of 

 the length of the animal. 



Pleon having the dorsal surface smooth. The first five somites subequal ; the sixth 

 about equal to the two preceding. 



Telson about as long as the rhipidura. 



Ophthalmopoda short, gradually increasing from the base, and not reaching beyond 

 the extremity of the first joint of the first pair of antennae. 



First pair of antennas about two-thirds the length of the animal ; the first joint a 

 little longer than the ophthalmopod, the second shorter than the first, and the third a 

 little longer than the first ; the flagellum is about twice the length of the peduncle, 



