10 DISCOVERY REPORTS 



Embryo. Single embryo, behind M. V at its point of lateral fusion with M. IV. 



Length. Up to 25 mm. 



Distribution of S. fusiformis. Recorded by other workers in nearly all oceans (see Thompson, 

 1948). Present data demonstrate that the southern limit to its distribution is the region of the sub- 

 tropical convergence. Data are insufficient to define its northern limit but it has been recorded at a 

 station in 63° 51' N., 16° 20' W., and also round the N. Cape of Iceland in September 1957 (Fraser, 



1959)- 



Salpa aspera Chamisso, 1819 (PI. I) 



Salpa aspera Chamisso, A. von, 18 19, De Animalibus quibusdam e classe Vermium Linnaeana, 



Fasc. I, De Salpa, 24 pp., PI. i (Berolini). 

 Salpa echinata Herdman, 1888. 

 Salpa runcinata-fusiformis Herdman, 1888 (part). 

 Salpa runcinata-fusiformis var. echinata Apstein, 1894a. 



Salpa fusiformis var. echinata Apstein, 18946; Apstein 1906 (part), 1908; Ihle, 1910. 

 Salpa fusiformis-runcinata form echinata Ritter, 1905; Ritter and Byxbee, 1905. 

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



Salpa fusiformis form aspera Ihle, 191 1; 1935; Metcalf, 1918; Sewell, 1926; Thompson, 1948. 

 Salpa fusiformis Yount, 1954 (part). 



Solitary Form (PI. la and c) 

 (Based on the examination of nine specimens) 

 External appearance. Similar to S. fusiformis, with more convex anterior. Posterior squarely 

 cut off with pronounced spinose processes. 



Test. (PI. I c) Serrated. Thin except for the thickened ridges which are similar in number and 

 disposition to S. fusiformis. Ridges characterized by denticulations of the test which give a serrated 

 appearance. Posteriorly the serrated ridges extend to pronounced spinose processes of the test. As in 

 S. fusiformis there are ten ridges defined as follows : 



(a) Four dorsal-limiting ridges, 



(b) Two dorsal-lateral ridges, 



(c) Two ventro-lateral ridges, 



(d) Two ventral ridges which originate posteriorly as a single mid-ventral ridge. 

 I shall refer to this arrangement of serrated ridges as ' simple '. 



Body muscles. Nine body muscles. M. I-III converge and fuse dorsally. M. IV-VII are parallel. 

 M. VIII-IX may approach but do not fuse medio-dorsally. 



Muscle fibres. Mean number 100-7 for M. IV, based on nine specimens. 



Alimentary canal. Compact oval nucleus. 



Stolon. Proceeds forward to about the level of M. VII where, turning left, it doubles back fol- 

 lowing the edge of the nucleus and emerging through the test on the right side of the nucleus between 

 M. VIII-IX. Length. Up to 95 mm. 



Aggregate Form (PI. lb) 

 (Based on the examination of twenty-nine specimens) 

 External appearance. Body barrel shaped with conical anterior and posterior protruberances of 

 the test. The latter show great variation in both their shape and length. None of the specimens showed 

 the ' fusiform ' appearance so characteristic of S. fusiformis. 



