PONTOGENEIIDAE i99 



but the figure shows it as rounded-quadrate ; in these specimens it is broadly rounded 

 exactly as in antarctica, Chevr. Every alternate flagellar joint of antenna i is enlarged and 

 bears sensory setae. The integument is covered with close-set lenticular impressions (or 

 scale-like imbrications, if preferred), more or less horizontal anteriorly, becoming vertical 

 (transverse) on the posterior segments. Pfeffer's description of the telson is correct, 

 except that it really is cleft ; a very slight pressure of the dissecting needle is enough to 

 separate the two lobes. 



Distribution. South Georgia. 



Pontogeneia antarctica, Chevr. (Fig. 118 h). 



Chevreux, 1906, p. 69, figs. 40, 41 ; 1913, p. 177, fig. 59. 



Chilton, 1912, p. 496; 1925, p. 178. 



? Non Stebbing, 1914, p. 364. 



Non Stephensen, 1927, p. 319, figs. 10, 11. 



Schellenberg, 193 1, p. 185. 



Occurrence: 1. St. 166. South Orkneys. Many $S, $$ and juv. 6-16 mm. 



2. St. 179. Palmer Archipelago. 7 $$ n-12 mm., 24 $$ 11-17 mm. 



Remarks. Integument with close-set elongate lenticular impressions, exactly as in 

 georgiana. Every 3rd flagellar joint of antenna 1 enlarged. 



I fail to find any characters separating this species from georgiana except the number 

 of joints separating every pair of enlarged joints on antenna 1. The anterior margin of 

 the head is the same in the actual specimens, though Chevreux's figure of this in 

 antarctica differs slightly, but not essentially, from that here given for georgiana. 



The straight line forming the junctions of the side-plates with the peraeon segments 

 in Chevreux's figure appears diagrammatic when compared with the actual specimens ; 

 Pfeffer's description and figure fit these specimens perfectly. It is of course only a 

 phenomenon of preservation, but many of these specimens exhibit the same loosely 

 articulated segments as described by Pfeffer in georgiana. 



Distribution. Graham Land; Petermann Island; South Shetlands; South Orkneys, 

 0-6 m. 



Pontogeneia tristanensis, n.sp. (Figs. 118 m, 120). 



Occurrence: St. 5. Tristan da Cunha. 3 $$ 6-7 mm., 2 $$ 7-9 mm., several juv. 3-5 mm. 



Description. Integument minutely shagreened, without pits. Postantennal angle 

 of head quadrate, the actual angle rounded. Eyes subcircular. None of the peraeon or 

 pleon segments dorsally dentate. Side-plates 1-4 shallow, 4 subtriangular, feebly 

 excavate on hind margin. Pleon segment 3 narrowing below on the pleural portion, 

 which is completely rounded on lower and hind margin. Telson twice as long as broad, 

 of nearly equal width throughout, cleft for one-quarter its length, lobes dehiscent, 

 apices narrowly rounded, no setules or spines. 



Antenna 1, flagellum with every 3rd or 4th joint in <$, every 4th joint in $, enlarged. 

 In the young every alternate joint is enlarged. 



