46 F. E. FRITSCH. 
BACILLARIE A. 
COSCINODISCACE®. 
Genus Metostra Ag. 
67. MerLosira sp. 
(Pl. III., figs. 148, 149, 1492.) 
Diam. cell = 7-9 »; long. cell. = 12-13 p. 
Hab.—On Phormidium on ice, four feet above frozen watercourse through 
“Penknife ice,” McMurdo Bay, September 13th, 1902. 
I have not been able to come to any satisfactory conclusions about the 
determination of this form. It occurred rarely (but then in considerable masses) on 
the surface of Phormidium at the above locality, and was always found dead. The 
valves were, in most cases, hemispherical, perfectly smooth (/.e. without markings of 
any kind), and there was generally a prominent constriction at the point of junction 
of the two valves (cf. the figures). Occasionally the line of junction of the valves 
showed a punctate structure lke a number of minute interlocking teeth (fig. 149a). 
Frequently the length of the valve was nearly equal to its breadth (fig. 149a), but 
sometimes the cells were appreciably longer (fig. 148) than wide. 
The frustules were generally isolated, as in the section Podosira of the genus ; 
but it does not appear to be related to any of the described species of that section. 
It is most like P. montagne: Kiitz., a much larger form, which has markings on its 
valves.» It may well be, however, that the frustules had fallen apart in the dead 
material, and that our form belongs to the section Lysigonium. 
The characters of the frustules agree fairly well with the descriptions of 
M. subflevilis Kiitz., given by Rabenhorst (Fl. Europ. Alg., 1. (1864), p. 39) and 
Micula (Kryptogamenflora v. Deutschland, Deutsch-Osterreich, etc., ii, 1 (1907), 
p. 153), but Kiitzing’s figure (Bacill. (1844), Tab. 2, fig. xiii.) shows the valves as far 
less convex than in the Antarctic form ; there is also practically no constriction and 
no indication of teeth at the line of junction of the valves (ef. op. cit., Tab. 2, fig. vi. of 
M. italica). Species like IM. lineata (Dillw.) Ag., and JZ salina Kiitz., should also be 
compared, It is possible that the Antarctic form is a new species, but the material 
was too inadequate to enable one to arrive at a definite conclusion on this point. 
