is8 DISCOVERY REPORTS 



Family LEPTOCYLINDRACEAE, Lebour, 1930 

 Genus Dactyliosolen, Castracane, 1886 



Dactyliosolen antarcticus, Castr. 



Castracane, 1886, p. 75, pi. ix, fig. 7; Karsten, 1905, p. 93, pi. ix, fig. 10. 



An important species in spring and autumn just to the south of the Antarctic con- 

 vergence. Frequently abundant farther south in the Weddell Sea after mid-season, but 

 rare in the Bellingshausen Sea. A species with a well-marked secondary autumnal 

 maximum. 



Dactyliosolen flexuosus, Mangin. 

 Mangin, 1915, p. 57, fig. 40. 



Similarly distributed but very much rarer than D. antarcticus. 



Dactyliosolen laevis, Karst. 



Karsten, 1905, p. 93, pi. ix, fig. 11. 



Moderately abundant on the spring survey round South Georgia, particularly in the 

 cold mixed water, mainly of western Weddell Sea origin, to the south-westward. Also 

 met with at several stations farther south, much more commonly in the Bellingshausen 

 than in the Weddell Sea. 



Genus Leptocylindrus, Cleve, 1889 



Leptocylindrus sp. 



A small form closely resembling L. minimus, Gran, of the northern hemisphere. It 

 was present at several stations far to the southward in both the Weddell and the 

 Bellingshausen Sea, always in small numbers, but was rare in the older Antarctic surface 

 water farther north. However, at one station to the north of Elephant Island it was 

 moderately abundant, and roughly one-ninth of the individuals appeared to be para- 

 sitized by Solenicola sp. 



Family CORETHRONACEAE, Lebour, 1930 

 Genus Corethron, Castracane, 1886 



Corethron pelagicum, Brun. 



Hustedt, 1930, p. 547, fig. 312. 



Present in sub-tropical water round South Africa in material not yet worked up in 

 detail ; only referred to incidentally in the present paper. 



Corethron valdiviae, Karst. 



Castracane, 1886, p. 85, pi. xxi, figs. 12, 14, 15; Karsten, 1905, p. loi, pis. xii, xiii; Mangin, 

 191 5, p. 50, fig. 54; Hustedt, 1930, p. 546. 



Mangin found it impossible to distinguish satisfactorily between this species and 

 C. inerme, Karst., owing to the presence of intermediate forms, and this is fully borne 

 out by our abundant material. Hustedt draws attention to the inadequacy of Castra- 

 cane's description and figures of the genotype C criophilum, and concludes that what 



