324 DISCOVERY REPORTS 



that is, they possessed markings characteristic of D. antarcticas at one end, and of D. 

 borealis at the other end of the same cell. It was not found in very cold water. 

 Observed at Sts. 451, 664, 666. 



"laevis" phase. (PL VI, figs. 2, 3.) 



Dactyliosolen laevis Karsten. 

 Karsten, 1905, p. 93, pi. 9, fig. 11. 

 Dactyliosolen flexuosus Mangin, 1915, p. 57. 



This phase is usually weakly siliceous, and varies from the preceding in the structure 

 of the connective zone. The intercalary segments usually are narrow and upon the 

 larger specimens squamose. The markings are indistinct, and are of the nature of short 

 striations arranged in the pervalvar axis. The striae do not cross completely over the 

 whole of the band, but fall short of the one margin, leaving a hyaline space. Diameter 

 of cell 20-40 ju ; pervalvar axis 90/i. 



Following the general habit of large polyphasic species-systems, specimens were ob- 

 served exhibiting the " antarcticus" phase at one end of a chain, and the "laevis" phase 

 at the other. Diphasic individuals, however, were not very common and the "laevis" 

 phase possessed a definite geographical distribution and probably is neritic. I include 

 in this phase Dactyliosolen flexuosus of Mangin. Mangin stated that he was unable to dis- 

 cover the fine longitudinal striation upon the connective zone but I have observed it 

 upon many specimens although it must be admitted that the majority are hyaline. The 

 flexuosity cannot be considered as a specific character, and is due probably to some 

 pathological defect in the cells. The phase was observed in considerable quantities 

 around South Georgia and the South Sandwich Group. 



Observed at Sts. 336, 337, 460, 461, 463, 475, 477, 478, 479, 505-513, 570; WS 545, 

 548. 549. 550, 55 1 * 552A. 



Dactyliosolen mediterraneus H. Peragallo. (PI. VI, figs. 4, 5, 6.) 



Peragallo, H., 1892, p. 104, pi. 13, figs. 8, 9. 



Hustedt, 1929, p. 556, fig. 317. 



Lauderia mediterranea Peragallo, H., 1888, vol. xxm, p. 81, pi. 6, fig. 45. 



Dactyliosolen meleagris Karsten, 1906, p. 160, pi. 29, fig. 2. 



Dactyliosolen Bergonii Peragallo, H., 1892, p. 104, pi. 13, fig. 6. 



Cells cylindrical, straight, usually united to form short chains. Valves flat or nearly so. 

 Connective zone composed of numerous intercalary bands. Bands of uniform width; 

 margins parallel, with shortly conical ends, not oblique, as in D. antarcticus. The ends 

 of the bands are arranged in a straight line one above the other, and do not form a spiral 

 as in the preceding species. Sometimes the ends of the bands are indefinite, giving the 

 cell wall an appearance of a continuous cylinder bearing a number of long marginal 

 decussate lines, penetrating to the centre. Bands covered with a fine areolation, areoles 

 rectangular, or nearly so, arranged somewhat in quincunx. Occasional bands are 

 hyaline. Diameter of cell 16-34/x ; pervalvar axis up to 80^. 



This species was observed at two stations only, to the south-east of Port Elizabeth. 



