The speeies are all included by Elu’cnberg in his genus
Gallionella.
a. Filaments not globuliferous.
* Extremities o f the cells serrated at the edges.
1. M e l o s e ir a a r e n o s a Moore, M S .
Plate X C I II . Figs. 2, 3.
Char. Y'AamQwta large, dark brown. YTw&tvX&a* twice or even
three times broader than long, divided in the centre hy a
double line.
Gallionella vai'ians Ehr., Die Infus. p. 167. t. 21. fig. 2.
Aleloseira arenosa Moore, MS. M. arenaria Ilalfs,
in Annals, vol. xii. p. 349. pl. ix. fig. 4.
Ilab. On a wet bank near Larne, co. Antrim : Mr. Moore.
Inner extremity of the Giant’s Causeway: Mr. W.
Thompson. Very sparingly in a stream near Shoreham,
Kent : Mr. Jenner.
This is by far the finest species of the genus, and is evidently
the plant which Ehrenherg had in view as the Alelo-
seira varians of Agardh, his description of that plant being as
follows : —
“ Corpusculis utrlnque planis, cylindricis aut nummifor-
mibus, a dorso glabris, a latere radiatim striolatis, ovariis
flavis aut flavo-viridihus.”
I t is probable, as Ehrenherg has correctly figured both
species, tha t he regarded the true Meloseira varians of Agardh
as the young state of his species.
The end surfaces of the frustules are closely applied to each
other, faintly marked with radiating striæ with their margins
serrated, the teeth of one frustule locking into those of the
other with which it is in contact, in the same manner as the
teeth of certain wheels are made to fit each other.
The name should be arenosa, and not arenaria.
* The term frustule, applied to the Diatomaceoe, has the same meaning
as the word cell used to describe the Confervoe.
2. M e l o s e ir a o r ic h a l c e a Kütz.
Plate X C I I I . Figs. 6, 7.
Char. Filaments rather slender, when recent o f a faw n colour,
Frustules two or three times longer than broad, twice
divided near the centre.
Kiitzing, in Linnæa, 1833, p. 71. fig. 68. Gallionella auri-
chalcea Ehr., Die Infus. p. 168. t. 10. fig. 6. ; Amer.
Bacil. part 2. p. 5. pl. xi. fig. 4 b.
Hab. In ditches and slow streams, Cheshunt : A. II. H.
Stevenston, Ayrshire : Rev. D. Landshorough. Dolgelly
: Mr. Ralfs.
This species differs from Meloseira varians, with which it
might be confounded, in its smaller filaments, different colour,
longer frustules, in the double division of these, and especially
in the dentated margins, by which M. orichalcea is related to
Meloseira arenosa, and which is the only character in common
between the two species. The Gallionella distans of Ehr.
comes close to this species, if it be not identical with it.
** Margins o f the cells smooth.
3. M e l o s e ir a variants Ag.
Plate X C I I I . Figs. 4, 5.
Char. Filaments rather thick, dark brown, becoming greenish
in drying. Frustules once or once and a h a lf as long as
hroad, once divided in the centre.
Ag. Conspect. Diatom, p. 64. ? Kiitz. in L in n sa , p. 71.
fig. 69. ; Harv. Br. Alg. p. 195. M. lineata Ag., Syst.
p. 8. ; Harv. in Manual, p. 195. Gallionella varians
Ehr., Die Infus. t. 10. fig. 4. G. aurichalcea Bailey,
Amer. Bacil. part 2. pl. 2. fig. 4 c. Conf. lineata Dillw.,
p. 44. t. ß Ju rg , Dec. 5. Xo. 18. Conf. hyemalis Jurg,
Dec. No. 17. No. 6. Vesiculifera composita Hassall, in
Annals of Nat. Hist. vol. x. p. 394. ; Ralfs, in Annals,
vol. xii. p. 350. pl. ix. fig. 5.