430 THE VOYAGE OF H.M.S. CHALLENGER. 



The structure of the external tissue is reticulate throughout, which is especially 

 noticeable in the rhipidura and dorsal crest. 



The rostrum corresponds somewhat to that of Sergestes spiniventralis, but the ventral 

 surface is not armed with a series of projecting teeth. 



North-east of the island of Juan Fernandez and about five hundred miles due west of 

 Valparaiso, another specimen of Sergestes was trawled at a depth of more than a mile and a 

 half, associated with specimens of Willemcesia, Pentacheles, and Glyphocrangon. It is 

 a mutilated specimen, but the existing parts correspond with those preserved of Sergestes 

 profundus, and as they are the only specimens in the collection that are recorded from so 

 considerable a depth, they are probably of the same species, and the description of one 

 may interpret the form of the other. The portion of the animal preserved is as far back 

 as the extremity of the second somite of the pleon with the appendages, but the body is 

 too compressed and disfigured to say more than that it is generally free from external 

 adornment. 



The rostrum is similar to that of the specimen from Station 137, and corresponds in 

 form, but in a less pronounced degree, with that of Sergestes spiniventralis. 



The ophthalmopoda are about one-fourth of the dorsal length of the carapace, and 

 somewhat clavate, but the ophthalmus is not of greater diameter than the stalk. 



The first pair of antennae has the first joint of the peduncle longer than the ophthalmus, 

 and the second and third joints subequal in length, and together as long as the first joint ; 

 the flagella are broken off. 



The second pair of antennae has the flagellum also wanting ; the scaphocerite is as 

 long as the peduncle of the first pair, moderately broad, and armed with a small tooth at 

 the outer distal extremity. 



The mandible is furnished with a long and slender synaphipod that reaches beyond 

 the frontal margins of the carapace and as far as half the length of the terminal joint of 

 the second pair of antennae. 



The oral appendages, so far as I have been able to examine them without dissection, 

 appear to correspond with those of Sergestes prehensilis. 



The first pair of gnathopoda is well developed and of generic value only ; the three 

 anterior free joints are fringed on the posterior margin, and the three distal joints on 

 the anterior margin, with long hairs. 



The second pair of gnathopoda are broken off at the coxal joint, which is broad and 

 robust. 



The first pair of pereiopoda is moderately long, and furnished with a prehensile 

 apparatus at the ultimate articulation. The second pair of pereiopoda is long and stout, 

 probably as long as the animal, the distal joints being fringed with long hairs. The 

 third pair of pereiopoda is similar to, but rather longer than the second. The fourth 

 pair is very nearly as long as the third, reaching beyond the carpal joints of the propodos; 



