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



characteristic of tho genus, the terminal ]>iu-t being subdivided into three articulations, 

 the first by far the longest, and having besides a distinct, though rather small terminal 

 claw. The exopods are very strongly developed, with exceedingly broad and muscular 

 basal parts. 



The caudal limbs are also very powerful, natatory, and agreeing in structure with 

 those in the male of Ambhjops ahhreviata. 



The telson (fig. 16) is rather short, attaining scarcely the length of the preceding 

 segment, and differs conspicuously from that in the typical species by the apex being 

 abruptly and broadly truncate, and even slightly emarginate in the middle, not as in that • 

 species narrowly rounded. It tapers very slightly, and has the outer part fringed with 

 numerous small denticles, those springing from the apical edge, about fourteen, being 

 somewhat more elongate. Moreover, in the middle of the apical edge is seen a small 

 tubercle, from which issue two slender and diverging setae. 



The uropoda exhibit the usual structure, and have the outer plate rather large, 

 almost twice the length of the inner. The latter is lanceolate, and projects considerably 

 beyond the tip of the telson. The auditory apparatus at the base of this plate would 

 seem to be quite rudimentary, whereas in the typical species it is well developed. 



Habitat. — The above described specimen was taken in the Southern Ocean off the 

 Crozet Islands, at a rather considerable depth. The locality is as follows : — 



Station 147.— December 30, 1873; lat. 46° 16' S., long. 48° 27' E. ; depth, 1600 

 fathoms ; Diatom ooze ; bottom temperature, 34° "2. 



Genus 4. Pseudomma, G. 0. Sars, 1869. 

 Pscudomma, G. 0. Sars, Nye Dybvands — Crustaceer fra Lofoten ; Christiaiiia Vid. Selsk. Forhandl., 1869. 



Generic Characters.- — Form of body slender, almost cylindrical throughout. Carapace 

 small, not covering by far the whole trunk, frontal margin evenly arched, without any 

 rostral projection. Eyes quite rudimentary, forming merely broad petaloid expansions 

 of the ocular segment, partly connate in the middle, and not exhibiting the slightest 

 trace of pigment or visual elements. Antennular peduncle very short ; male a^jpendage 

 large, conical. Autennal scale more or less obliquely truncate, with inner corner pro- 

 jecting, outer jutting forth as a strong dentiform process. Gnathopoda having endopod 

 powerfully developed, with terminal joint densely hirsute. Legs exceedingly slender 

 and fragile, filiform, increasing in length posteriorly ; propodal joint subdivided into 

 three articulations, terminal joint obtuse and densely hirsute, not unguiform. Sexual 

 appendages of male very narrow, with a single apical bristle. Caudal liuil)s in male all 

 natatory. Telson Unguiform, with apex entire, apical spines elongate. Inner plate of 

 uropoda shorter than outer, with auditory apparatus distinctly developed. 



Reuiarks. — Of this genus, chieHy distinguished by the peculiar rudimentary condition 



