DESCRIPTION OF THE SPECIES n 



Test. Serrated. Denticulations irregular in their distribution. 



Body muscles. Six body muscles. M. I-IV and M. V-VI fuse dorsally to form two dorsal muscle 

 groups. M. IV-V approach laterally but do not fuse. 



Muscle fibres. Mean number 194-1 for the total of M. I-VI, based on twenty-nine specimens. 



Alimentary canal. Compact oval nucleus. 



Embryo. Single, as in 5. fusiformis. 



Length. Up to 60 mm. 



Distribution of S. aspera. Present data show its occurrence north of the subtropical convergence 

 in Atlantic, Pacific and Indian Oceans. 



Yount (1954, pp. 303-4) has drawn attention to the similarity between S. maxima Forskal and the 

 serrated form of S. fusiformis {= S. aspera) and suggests that these species may have been confused 

 in the literature. Specimens of the aggregate form of S. maxima examined in the course of the present 

 study have differed from S. aspera in having a most pronounced bulbous thickening of the test, 

 ventral to the nucleus; while the solitary form is quite distinct in the absence of dorsal fusion of 

 M. I-III, M. I-IX being in fact more or less parallel (see Thompson, 1946, Pis. 68 and 69). Spinose or 

 serrated specimens of S. maxima have not occurred so far in the collections examined and the serrated 

 specimens of this species figured by Yount (ibid. p. 301, fig. 13 and p. 302, fig. 14) I consider likely to be 

 S. aspera. 



Salpa thompsoni sp.nov. (PI. II) 

 [?] Salpa antarctica Meyen, 1832. 

 Salpa echinata Herdman, 1888 (part). 

 Salpa runcinata-fusiformis Herdman, 1888 (part); 1910. 

 Salpa fusiformis var. echinata Apstein, 1906 (part). 

 Salpa runcinata-fusiformis var. echinata Herdman, 1910 (part). 

 Salpa fusiformis aspera Mackintosh, 1934; Hardy and Gunther, 1935. 



HoLOTYPE. A specimen of the solitary form 71 mm. long taken in a i m. net towed obliquely 

 (N looB) between 89 m. and the surface at Discovery station 2144, 48° 04-3' S., 101° 07-2' E. on 

 II December 1937. 



Registration number. British Museum (Nat. Hist.), i960. 10. 18. 5. 



Body proportions. Total length 75 mm., body length 71 mm., nucleus length 15 mm. 



Muscle-fibre number. 89 fibres in M. IV. 



Stolon. Stolon with two fully differentiated blocks of buds : 



Block I. 144 buds, blastozooids 3 mm. long 

 Block 2. 230 buds, blastozooids i mm. long. 



No evidence that previous release of buds has occurred (see p . 25 ). Stolon extends forward to level of M . V. 



Allotype. A specimen of the aggregate form 20 mm. long taken in a i m. net towed obliquely 

 (NiooB) between 91 m. and the surface at Discovery station 1906, 53° 54-6' S., 63° 58-1' W. on 

 30 November 1936. 



Registration number. British Museum (Nat. Hist.), i960. 10. 18.6. 



Body proportions. Total length 34 mm., body length 20 mm., nucleus length 5 mm. 



Muscle-fibre number. 188 fibres for the sum of M. I-VI counted along the right side. 



Embryo. Single oozoid present. 



Paratypes. Ten specimens of the solitary form taken in a i m. net towed obliquely (NiooB) 

 from 122 m. to the surface at Discovery station 2574, 47° 59-9' S., 19° 56-2' E. on 3 February 1939. 



Registration number. British Museum (Nat. Hist.), i960. 10. 18.7. 



