302 DR THOMAS SCOTT ON THE 



The fifth pair are somewhat similar to those in Porcellidium ravanse, both in their 

 general outline and in having their extremity bluntly rounded (fig. 10). 



The abdomen and caudal rami also resemble the same parts in P. ravanse, but 

 in that species the caudal rami do not reach to the end of the fifth pair of feet, 

 whereas in the present form the caudal rami reach somewhat beyond these appendages. 

 They are also more bluntly rounded at the end, and the terminal and marginal spines 

 are somewhat differently arranged, as shown in the drawing (fig. 12). 



Male. The male, as is usual, is smaller than the female ; the antennules are 

 modified for grasping ; the fifth pair of feet are different in form and armature, and 

 the abdomen and caudal rami are shorter (see figs. 12 and 13). 



The fifth pair of feet are small, and narrow at the proximal end, but they become 

 wider distally ; the extremity is obliquely truncated and fringed with about six short 

 setiferous spines (fig. 11). Caudal rami are very short, and have the squarely 

 truncated ends furnished with a few marginal setae (fig. 13). 



Habitat. Scotia Bay, South Orkneys; collected in June 1903; Station 325, 

 60 43' 42" S., 44 38' 33" W. 



Remarks. This species, as already stated, has some resemblance to Porcellidium 

 ravaiKP, Thompson & A. Scott, but differs in several anatomical details, as, for example, 

 in the structure of the female antennules, as well as in the form and armature of the 

 caudal segments. It also resembles in some respects the Porcellidium ivolj'endeni 

 described by G. S. BRADY.* 



Genus Tisbe, Lilljeborg.t 1853. 

 Tisbe austrina, new species. (PI. III. figs. 26-30.) 



Female. This species, in its general appearance, is somewhat like Tisbe minor 

 (T. Scott), but is rather more slender. Length about 0'6 mm. 



Antennules composed of eight joints ; the second and third joints are subequal and 

 of moderate size; the fourth is fully half as long as the third; the fifth and sixth, 

 which are subequal, are together about as long as the fourth, but the seventh is very 

 small ; the end joint was incomplete, but appeared to be about as long as the fourth 

 joint. The antennae are small, and the outer ramus reaches only to the end of the 

 second joint of the inner ramus. Mouth organs somewhat similar to those in Tisbe 

 minor, but the second maxillipedes are moderately stout. All the four pairs of 

 swimming legs are also somewhat similar to those in the species mentioned. 



In the fifth pair, the inner portion of the basal joint ends in a blunt pointed apex, 

 which bears two setse, one being moderately stout and elongated, and the other small ; 



* Deutsche Sudpolar Exped., 1901-1903 : "Uber die Oopepoden der Stamme Harpactieoida," et seq., p. 556 (1910). 

 Separate reprint. 



t " The name Idya having been previously given by RLAINVILLE to a genus of Acalephic,"' was changed by G. O. 

 SAHS to Idyxa : see Kept, of Second Norwegian Arctic Exped. in the " Fram," 1898-1902, No. 18 ; Crustacea, by G. O. 

 SARS, p. 21 (1909). Rev. T. R. R. STEBBING, in Annals of the South African Museum, vol. vi. p. 544 (1910), restores 

 Lilljeborg's name, Tisbe. 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 548.) 



