TIRONIDAE 



149 



carina produced posteriorly into a tooth, which increases in size posteriorly, that on 

 segment 5 being the largest; segment 6 feebly carinate, ending in a very small median 

 tooth at base of telson. Postero-inferior angle of pleon segment 3 quadrate, with a very 

 slightly produced point; a few widely-spaced setules on hind margin above the angle. 

 Telson with a minute setule in a notch on apex of each lobe, and four to five setules 

 on upper surface. 



Antenna 1, flagellum 10-jointed, accessory flagellum 4-jointed. Antenna 2, flagellum 

 10-1 i-jointed. Maxillary palp not much widened. Maxilliped, outer plate with margin 

 convex. 



Gnathopods 1 and 2 and peraeopods 1 and 2 as in acanthurus. Peraeopods 3 and 4, 

 2nd joint obovate, wider distally, hind margin with a few crenulations, each notch with 

 a setule. Peraeopod 5, 2nd joint broadly expanded, subcircular, hind margin crenulate, 

 4th joint strongly expanded on hind margin. 



Remarks. A species resembling thompsoni in the unidentate pleon segments, 

 acanthurus in the telson and general features, but distinguished from all the three species 

 of the genus by the 5th peraeopod. 



Genus Syrrhoe, Goes. 

 Stebbing, 1906, p. 281. 

 Sexton, 191 1, p. 202. 

 Monod, 1926, p. 54. 



Syrrhoe psychrophila, Monod (Fig. 87). 



Monod, 1926, p. 54, fig. 52 (crenulata, var.). 

 Schellenberg, 1931, p. 159, fig. 83. 



Occurrence: 1. St. 45. South Georgia. 2 $$ 12 mm. 



2. St. 140. South Georgia. 2 $$ 9 mm., 2 $? 8-9 mm. 



3. St. 144. South Georgia. 1 cj 10 mm., 5 $? 8-10 mm. 



4. St. 156. South Georgia. 1 $ 10 mm., 1 juv. 7 mm. 



Remarks. Monod distinguishes the Antarctic variety mainly by 

 the gap in the denticulation on the posterior margin of pleon seg- 

 ment 3 ; the other two characteristics seem likely to be inconstant. 



The present specimens have no denticulation on peraeon seg- 

 ment 7 or on pleon segment 4. The denticulation on pleon segment 

 3 is interrupted laterally. Typical crenulata has the 7th peraeon segment denticulate 

 on the posterior margin. Presumably psychrophila resembled crenulata iri this respect. 

 Moreover, since Monod does not mention it among the differences separating the 

 northern and southern forms, the hind margin of the 2nd joints of peraeopods 3-5 was 

 presumably serrate as in Sars' figure (1895, pi. cxxxvi) of crenulata. In the present 

 specimens these serrations are much smaller and more widely spaced, thus approaching 

 semiserrata. 



Side-plate 2 narrowing below to a rounded apex, not truncate as in crenulata and 



Fig. 87. Syrrhoe psychro- 

 phila, Monod. Second 

 joint of peraeopod 5. 



