REPORT ON THE CRUSTACEA MACRTJRA. 411 



" The second pair of gnathopoda 1 at least two-thirds the length of the entire animal. 



"Sixth somite of the pleon nearly one-fifth of the length of the animal, equal to 

 the fourth and fifth somites combined, and nearly as long as the three anterior somites 

 united ; it is twice as long as broad and not much longer than the telson. 



" Pleopoda very long and slender. 



" Rhipidura having the external margin of the outer branch armed about midway 

 with a sharp tooth, but rather nearer the base than the apex." 



Habitat. — Cape York ; north of New Guinea ; North-West Pacific ; Greenland 

 (K rover). 



Carapace about one-third the length of the animal. Rostrum horizontal, slender, but 

 not very long, reaching to about one-third the length of the ophthalmopod. 



Pleon having the five anterior somites subequal, and the sixth nearly equal to the 

 united length of the three preceding ; dorsal surface unarmed, excepting that the posterior 

 margin of the ultimate somite projects posteriorly as a small point. The sixth somite 

 is about half as deep as long, and has the inferior margins fringed with ciliated hairs, 

 which gradually increase in length and thickness posteriorly. 



The telson is long, narrow, and tapers slightly to the extremity, which terminates in 

 a small fork ; the margins are thickly fringed with long ciliated hairs that are continuous 

 to the extremity. 



The ophthalmopoda are about one-half the length of the carapace, reaching as far 

 as the extremity of the first joint of the peduncle of the first pair of antennae. The 

 ophthalmus is about twice the greatest breadth of the stalk. 



The first pair of antenna? has the peduncle about as long as the carapace, and 

 terminates in a slender flagellum that makes the entire organ equal in length to the 

 animal ; the first joint is the longest, and about equal to the second and third 

 together ; the second is only slightly shorter than the third ; the third supports a long 

 and slender flagellum that is enlarged at the base into a strong bulb, which supports a 

 series of membranous cdia, and a small secondary feeble and immature branch. 



The second pair of antennae has the ultimate joint of the peduncle very long, equalling 

 that of the first joint of the peduncle of the first pair, and supports a long and slender 

 flagellum, a large portion of which is broken off, so that its length in the Challenger 

 specimens cannot be determined. The scaphocerite is long and broad, reaching quite to 

 the extremity of the second joint of the peduncle of the first pair of antennas ; the outer 

 margin has a small tooth near the extremity, and the inner margin is fringed with strong 

 ciliated hairs. 



The first pair of gnathopoda is rather smaller than usual. 



1 Pes maxillaris tertius bessem longitudinis totius animalis minime xquans, in Kroyer's description, is undoubtedly 

 homologous with the second pair of gnathopoda, and not with the third pair of maxilla' (or maxillipedes). 



