SYNONOMY AND PREVIOUS DESCRIPTIONS 7 



laterally. Apstein's data covered a wide geographical range, and since the serrated form tended to 

 occur in the colder waters (p. 269, figs. 5-6) he concluded that the form echinata was a cold-water 

 variant of the type occurring in both aggregate and solitary form. Apstein, however, remarks (p. 250) 

 that the differences between the form echinata and the type show great variation. This, together with 

 the fact that the collection was from a wide geographical area, including subantarctic and antarctic 

 material, suggests that there was a confusion of species. It will be shown later (p. 22) that the specimen 

 of the solitary form (Text-fig. 6) is typical of a species limited in its distribution to the Southern 

 Ocean, while the aggregate form (Text-fig. 4) shows characters associated with a species that occurs 

 only in waters north of the subtropical convergence. 



Farran (1906) in an oft-quoted paper described the serrated form in Irish waters from specimens 

 of the aggregate stage. His statement that the musculature was the same as that of the type refers 

 to specimens of the aggregate stage only, but it has frequently been quoted as referring to the solitary 

 form as well (Thompson 1948 p. 158). 



The serrated form of S. fusiformis has subsequently been described from collections made by most 

 expeditions, and references are to be found in Apstein (1908); Ihle (1910, 191 1, 1912); and Murray 

 and Hjort (1912), and others. Ihle (191 1, p. 587) used for the first time the name S. fusiformis aspera 

 to designate this serrated form. 



From a small collection of material collected by the Belgica Expedition van Beneden and Selys- 

 Longchamps (191 3) described in a rarely quoted paper a new variety of S. fusiformis which they called 

 S. fusiformis Gerlachei. Their description, based on one specimen each of the solitary and aggregate 

 forms, is most thorough and detailed, and a comparison is made between their specimens and 

 Herdman's (1888) and Ritter's (1905) descriptions of 5. echinata and S. fusiformis-runcinata. The 

 solitary form of S. fusiformis Gerlachei differs from S. echinata in having M. VIII and IX joined and 

 having a highly serrated test with a medio-dorsal serrated ridge. Some of the differences they describe, 

 such as the lack of a 'cephalic projection' in the aggregate form, are probably variations attributable 

 to wear or damage but the major characters of muscle arrangement and test structure they found 

 incompatible with the published descriptions of S. echinata and S. fusiformis-runcinata. They suggest 

 (p. 119) that these differences are characteristic of a form, variety or species endemic to the part of the 

 Antarctic from which they came, although they agree that on such limited material the possibility of 

 individual variation cannot be ruled out. 



Metcalf (191 8) in his classic paper on the Salpidae of the Philippines concludes that the specimens 

 of S. fusiformis aspera in his collection showed a complete intergradation between smooth and the most 

 spinose test. His figure of the solitary form is of interest because it seems to combine the test characters 

 of Ritter (1905, fig. 14) based on specimens from the San Diego region, and the musculature of 

 Apstein (1906, fig. 6) based on antarctic specimens — a combination not found in any of the specimens 

 to be described in this paper. 



Sewell (1926, p. 76) reviews briefly previous records of S. fusiformis aspera and their interpretation 

 and concludes that ' it seems impossible to justify any separation, even as a distinct form, of those with 

 spinose test from those with a smooth one, though it is possible that Ritter and Farran are right in 

 their belief that the spinose character is a mark of age'. This view is favoured by Thompson (1948) 

 while Yount (1954) goes further and groups all the variants together as S. fusiformis. 



The works described above are those relevant to the problem of the serrated form of S. fusiformis 

 and the various conclusions of the authors cited may be summarized as follows. 



(i) New species: Chamisso, 1819; Herdman, 1888. 



(2) A subspecies (of which there may be others): van Beneden & Longchamps, 191 3. 



(3) Cold-water form; Apstein, 1906. 



