56 



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

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

 edge very obli([ue and indistinctly defined, dactylus slender. Posterior 

 gnathopoda of the iTsual strnctnre, pro})od(i.s short, scarcely produced beneath 

 the small dactylus. Pereiopoda rather slender, basal joi)it of the 3 posterior 

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

 with a digitiform supplementary ramus and a few short lobes at the ojiposite 

 side; a 5tli pair of small branchial lamellse present. Last pair of urojioda 

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

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

 a distinct tei'minal joint. Telson oblong, deeply cleft. 



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

 guished from the other Lysianassid genera Ijotla by the outer habitus and b\' 

 several anatomical characters, among others by the ^•ery slender form of the 

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

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

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

 to be described in the following pages, the oth being the Li/sianasba ahi/ssi 

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

 Challenger Expedition. The genus PJatamon of tlie latter author is very 

 nearly related to the present genus, only differing l)y a somewhat different 

 structiu-e of the posterior gnathopoda. 



15. Hippomedon denticulatus, (.Sp. Bate). 



(PI. 20). 



Anoni/x dcntkulntus, Sp Ba^e, Cat. Ampliip (.'ru.'^t. Brit. JIiis. p 75. 



Syn; Hippomedon Holbolli, Boeck ^not Kviiyer). 



Body glabrous, compressed, luit witli the back evenly vaulted. 

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

 lateral corners but slightly projecting, acute. Fii'st pair of coxal plates much 

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

 to obtect the buccal mass laterally; 4t]i 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 ejjimeral plates of metasome 

 jutting out posteriorly as a narrow lanceolate upturned projection defined 

 from the posterior edge by a distinct incision. Fii'st 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; 2'ig™P"f light red witli a few opake white stri])es transversally. 



