COLLECTED IN THE SOUTH ORKNEYS, 335 
56. CosciNopISCUS. RADIATUS, Ehrenb. (1838); Rabenhorst, Fl. Europ. Alg. 
i, 1864, p. 34 
Samples 4 and 6 (red snow !). isolated. Previously recorded from 
Kerguelen ( Hooker § Harvey). 
A small form (diam. valv. =40-60 д), otherwise agreeing with the existing 
descriptions. 
57. TRICERATIUM sp. 
Sample 4 (red snow !) ; only a single dead individual seen, but fragments 
of the valves common. 
The single individual seen closely resembled Van Heurck’s (Atlas, pl. 112. 
g. 1) and Wolle's (Diatomacee of Nor th America, pl. 105. fig. 8) figures of 
$ arcticum, Bright, in the character of the arcolæ (small at the 3 corners !); 
the general shape was more that of 7. repletum, Grev., var. balearica, Grun. 
(Van Heurck, loc. cit. pl. 110. fig. 7). 
58. SYNEDKA sp. 
Sample 11, rare. 
59. EcxoriA GRACILIS, W. Smith, Brit. Dial. i. 1853, p. 16 & pl. 30. 
fig. 249. 
Sample 9, rather common. 
A form with but very slightly recurved ends. Length. of valve =22 p ; 
breadth 24 
60. CoccoxEIs COSTATA, Greg. Trans. Mier. Journ, у. 1857, p. pl. 1. 
fig. 27 
Samples 9 and 10, rare. 
61. NAVICULA BOREALIS (Lhrenb.), Каз. 5 Van Heures, Synopsis Liat, 1885, 
р. 76, pl. 6. fig. 3 
Samples 4, rare ; 9, 15, and 17, rather common. Previously recorded 
from Cockburn Island (Hooker $ Harvey). 
Length of valve about 40  ; breadth 9 p. 
62. Navicuta Braunu, Grun.; Van Heurck, loc. cit. p. 19, pl. 6. fig. 21. 
Sample 10, very rare. 
Length of valve =37 ш; breadth —12 р 
63. NavievraA Вквіххохи, Kütz., var. DIMINUTA, Van Heurck, loc. cit. p. 77, 
pl. 5. fig. 8. 
Samples 9, 10, 13, and 15, rather common. 
Length of valve 220-344; breadth =5-6 ш 
