8 DISCOVERY REPORTS 



(4) Old-age variant : Ritter, 1905; Farran, 1906. 



(5) No recognizable variety or form: Sewell, 1926; Yount, 1954. 

 It is perhaps not surprising in view of these differing conclusions that the overall picture of the 



geographical range of S . fusiformis extends from 60° N. to 65° S. (Thompson, 1948). Few, however, 

 of the above papers are based on adequate subantarctic and antarctic material and it is significant that 

 where specimens were available, well-serrated animals are described in which the solitary form has 

 M. VIII and IX joined dorsally (Apstein, 1906; van Beneden, 1913), while in some cases specimens 

 of the aggregate form are described in which M. IV and V are joined laterally (Herdman, 1888; 

 van Beneden, 1913). 



It will be realized from the above that previous authors have attached varying taxonomic importance 

 to different morphological features. When any one of these features, such as the external character of 

 the test, has been considered on its own, such differences as occurred, particularly in those collections 

 of material that cover a wide geographical range, have invariably been attributed to individual 

 variation within a single species. The data to be presented here will show that it is possible by con- 

 sidering variation in a complex of characters to distinguish four species. These species have been 

 variously confused in the literature of the group. 



DESCRIPTION OF THE SPECIES 

 Salpa fusiformis Cuvier, 1804 (Text-fig. la, b) 



Salpa maxima variety Forskal, 1775. 



Salpa fusiformis Cuvier, G., 1804, Ann. Mus. Hist. Nat., An. xii, Tome 4, pp. 360-82, pi. 68; 

 Apstein, 1894^, 1901, 1906; Farran, 1906; Streiff, 1908; Ihle, 1910, 1935; Sigl, 1912; Bomford, 

 1913; Metcalf, 1918; Sewell, 1926, 1953; Thompson, 1948; Yount, 1954 (part); Bernard, 

 1958; Fagetti, 1959. 



Salpa runcinata Chamisso, 1819; Brooks, 1893. 



Salpa maxima Meyen, 1832. 



Biphora depressa Sars, 1829. 



Biphora tricuspidata Sars, 1829. 



Salpa runcinata-fusiformis Krohn, 1846; Traustedt, 1885; Herdman, 1888; Apstein, 1894a. 



Salpa fusiformis-runcinata Ritter, 1905; Ritter and Byxbee, 1905 (part). 



Salpa fusiformis fusiformis IhXc, 191 2; Stiasny, 1926. 



Salpa fusiformis f . typica Michaelson, 191 5. 



Solitary Form (Text-fig. la) 

 (based on the examination of fifty-three specimens) 



External appearance. Elongate, with a slightly convex anterior and a squarely cut off posterior. 

 In section the anterior is subcylindrical with a flattened dorsal surface, while the posterior is triangular. 

 The mouth and the atrial apertures are terminal. 



Test. Smooth, firm and transparent. Thin, except where thickened to form characteristic ridges. 

 From the posterior dorsal edge, starting at two spinose processes of the test there are the left and right 

 dorsal limiting ridges which, proceeding forward, soon divide into outer and inner branches. Lateral 

 ridges, also originating in posterior processes, form the edges to the dorsal surface. A ventro-lateral 

 ridge runs below each dorsal edge while posteriorly there is a well-marked keel-like mid-ventral ridge 

 which, directed forward, divides to form two ventral limiting ridges. 



Body muscles. Nine body muscles. M. I-III and M. VIII-IX converge and fuse medio-dorsally. j 

 M. IV-VII are parallel. 



