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



The telson is as long as the lateral plates of the rhipidura ; it is dorsally flattened 

 and laterally compressed, the longitudinal angles being armed with four small spines on 

 each side, and terminates in two long outer and two small inner spines. 



The ophthalinopoda are short, thick and orbicular. 



The first pair of antennae has the peduncle short, the first joint being furnished with 

 a short, sharp pointed stylocerite. The nagella are scarcely longer than the rostrum. 



The second pair of antenna? carries a long, narrow scaphocerite, which tapers to the 

 distal extremity and is armed with an external apical tooth, and bears a flagellum as 

 long as the body of the animal. The appendages are slender, tolerably robust, and not 

 of extreme length. 



The pleopoda are short and strong, and the posterior pair, which helps to form the 

 rhipidura, is not longer than the telson ; the outer plate is longitudinally grooved, and 

 furnished with a perfect diaeresis, the outer limit of which is defined by a small spine. 



Observations. — The close resemblance of the specimens taken by the Challenger in 

 the Oriental Archipelago to those found at the West Indies, and, therefore, on the 

 opposite side of the globe, is a matter of interest, since this species has not yet been 

 found at any intermediate locality, and does not inhabit depths greater than about 500 

 fathoms. 



Plesionika, n. gen. 



Carapace smooth ; dorsally carinated anteriorly, and produced to a long, narrow, 

 laterally compressed rostrum, which as well as the frontal crest is armed with teeth. 



Ophthalmopoda Inarticulate. 



First pair of antennas armed with a sharp point and a wide stylocerite, and terminating 

 in two long slender flagella. 



Second pair of antennas terminates in a long and slender flagellum, and carries a long, 

 narrow scaphocerite, that is armed on the outer side with a strong subapical tooth. 



Mandible having a three-jointed synaphipod ; psalistoma well developed and distinct 

 from the molar tubercle. 



Second pair of gnathopoda pediform, and destitute of a basecphysis. 



First pair of pereiopoda slender and simple, terminating in a small styliform dactylos. 

 Second pair long, slender, and minutely chelate, the carpos being long, flexible and multi- 

 articulate. Three following pairs long, slender, and simple, remarkable for the great 

 length of the carpal and propodal joints. 



Pleon about three times as long as the carapace, and terminating in a long, narrow 

 and tapering telson, the sides of which are depressed. Pleopoda long, carrying flat sub- 

 foliaceous rami ; outer plates of the rhipidura subecmal with the telson. 



The branchiae are well developed and differ from those of Pandalus in having a 



