234 DISCOVERY REPORTS 



Subfamily MELOSIROIDEAE 



Genus Melosira Agardh 

 Agardh 1824 



The generic name was originally spelt Meloseira. 



Melosira polaris Grunow. 



Grunow 1884, vol. xlviii, p. 95, pi. E, fig. 33. 

 Hustedt, 1928, p. 273, fig. 116. 



Cells discoid, united in short chains, valves flat or nearly so, radial furrows strongly 

 marked, extending to one-third of the diameter of the valve, radial lines of fine pearls 

 alternating with the furrows. 



Diameter of valve 26-35/x, pervalvar axis 5-8^. 



This plant was observed in small numbers together with Melosira sol in the Bransfield 

 Strait. A tychopelagic form, seldom in the plankton. This species has been observed 

 in northern waters, but is not common, littoral. 



Observed at St. WS 481. 



Melosira sol (Ehrenberg) Kiitzing. 



Kiitzing, 1849, P- 3 1 - 

 Karsten, 1905, p. 70, pi. 1, figs. 3-9. 

 Hustedt, 1927, p. 270, fig. 115. 

 Gallionella sol Ehrenberg, 18446, p. 202. 



Cells discoid, strong, united to form chains, often of considerable length. Valves 

 flat, or very weakly concave. Valves furnished with radial furrows occupying fully half 

 the radius, peripheral zone finely striate, central area without structure. Margin of 

 valve furnished with a single line of pores, girdle short, valve mantle finely striate, 

 striae moniliform. Chromatophores : numerous flat plates. Diameter of valve 44-90^ , 

 mostly 66^; pervalvar axis 8-12/^. 



A very variable species widely distributed throughout the temperate zone, although 

 not frequently met with in English waters. Observed in fair numbers in the Bransfield 

 Strait, and again off the Falkland Islands. A tychopelagic form. 



Observed at Sts. WS 1 01, 481. 



Melosira sphaerica Karsten. 



Karsten, 1905, p. 70, pi. 1, fig. 2. 

 Mangin, 1915, p. 68, fig. 47. 



Cells shortly cylindrical, valves circular, united to form short chains of some four to 

 eight cells. Cells weakly siliceous, chains irregular, valves without any definite structure. 

 Chromatophores: several small plates. Diameter of valve 54-65/x, mostly 60/^; per- 

 valvar axis 60/x. 



It is probable that this species is not a true Melosira. The cells are so weakly siliceous 

 that when allowed to dry they collapse, and no satisfactory mounts can be made of them. 

 A characteristic Antarctic form. A neritic diatom but never found in large quantities. 



Observed at Sts. 305, 460, 501, 508, 509, 510, 575. 



