56 



slightly reaching beyond the masticatory lobe; terminal joint claw-like. Anterior 

 gnathopoda very slender, carpus elongated, propodos oblong ovate, palmar 

 edge very oblique and indistinctly denned, dactylus slender. Posterior 

 gnatliopoda of the usual structure, propodos short, scarcely produced beneath 

 the small dactylus. Pereiopoda rather slender, basal joint of the 3 posterior 

 pairs large and laminar. Branchial lamellae of 3rd and 4th pair provided 

 with a digitiform supplementary ramus and ai few short lobes at the opposite 

 side; a 5th pair of small branchial lamellaB present. Last pair of uropoda 

 considerably projecting beyond the preceding pair; rami elongated, subequal, 

 not setous, but armed with small denticles on the edges, the outer one with 

 a distinct terminal joint, Telson oblong, deeply cleft. 



Remarks. The present genus, established by Boeck, is well distin- 

 guished from the other Lysianassid genera both by the outer habitus and by 

 several anatomical characters, among others by the very slender form of the 

 inferior antennae and of the anterior gnatliopoda. The eyes are imperfectly 

 developed and disappear, as a rule, completely in specimens preserved in 

 alcohol. In the northern Ocean occur 5 species of this genus, 4 of which are 

 to be described in the following pages, the 5th being the Lysianassa abyssi 

 of Goes. Besides, the Rev. Mr. Stebbing has described 4 species from the 

 Challenger Expedition. The genus Platamon of the latter author is very 

 nearly related to the present genus, only differing by a somewhat different 

 structure of the posterior gnatliopoda. 



15. Hippomedon denticulatus, (Sp. Bate). 



(PL 20). 



Anonyx denticulatus, Sp Ba^e, Cat. Amphip Crust. Brit. Mus. p 75. 

 Syn: Hippomedon Holbolli, Boeck (not Kroyer). 



Body glabrous, compressed, but with the back evenly vaulted. 

 Cephalon scarcely as long as the 2 first segments of the mesosome combined, 

 lateral corners but slightly projecting, acute. First pair of coxal plates much 

 broader than the succeeding pair, and dilated inferiorly so as completely 

 to obtect the buccal mass laterally; 4th pair about twice as deep as the 

 body, forming posteriorly an acute-angled projection; 5th pair comparatively 

 small, broader than they are deep. Last pair of epimeral plates of metasome 

 jutting out posteriorly as a narrow lanceolate upturned projection defined 

 from the posterior edge by a distinct incision. First segment of urosome not 

 forming any dorsal projection. Integuments smooth, without any distinct 

 sculpturing. Eyes narrow, linear, slightly widened below, with no trace of 

 lenses; pigment light red with a few opake white stripes transversally. 



