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4 2 4 DIATOMACEÆ.
entangled. Frustules short, triangidar, loith two conspicuous
puncta at the end. Lateral surfaces ohovate or
sub-clavate.
^ Frustules scattered, more Jirmlg attached to the stipes,
ivhich is more evident.
Grev. in Hook. Br. Fl. vol. ii. p. 409. ; Harv. Br. Alg.
p. 207. Gomph.? olivácea Y\w., Die Infus. 218. t. 18.
f. 9. ; Pritch. Infns. p. 228. Exilaria minutissima
Berk., Br. Alg. p. 22. t. 7. f. 1. Aliridion vernale Ag.,
Consp. Diatom, p. 556. f. 31. Gomph. geminatum
Kiitz., Alg. Aq. clulc. No. 13. Gomph. Leiblini Kiitz.,
Synop. Diatom, p. 568. fig. 46.
Hah. On stones, &c., in freshwater spring, King’s Cliff,
Northamptonshire : Rev. AI. J. Berkeleg. Henfield, Sussex
: Air. Borrer. Mayfield, Sussex : Air. Jenner. Yarmouth
: Air. Dawson Turner. River Severn, near
Shrewsbury : Air. Leighton. Cheshunt, Herts, and River
Lea : A. II. H. A t the base of Bandon Mountains :
Air. Andrews. — /3. Duddingston Loch : Dr. Greville.
The stipes in the species in its ordinary state, owing to its
being imbedded in a mucous matrix, is often with difficulty
discernible. The frustules approach rather closely to those
of Gomph. dichotomum ; than which, however, they are shorter,
broader, and more decidedly cuneate.
7. Gomphonema minutissimum Ag.
Plate C. Fig. 3.
Char. Frustules curved, striated; terminal puncta well
marked. Lateral surfaces clavate, striated.
Kiitz. Syn. Diatom, p. 567. fig. 43. ; Ehr. Die Infus.
p. 219. t. 18. fig. 5. ; Pritch. Infus. p. 228. Gorriph.
curvatum Kiitz., Syn. Diatom, p. 567. f. 51. ; Kiitz.
Aq. dulc. No. 76.
Hah. Shrewsbury : Air. Leighton. Slioreham, Kent :
Air. Jenner. Cheshunt : A. II. II. Near Dublin : Prof.
G. J. Allman. Swansea ; Air. Ralfs.
“ This species differs from all the foregoing in its curved
frustules, in having a notch on one only of the lateral mai'gins
and two striæ passing down the frustule and coimccting the
upper and lower puncta.” — Ralfs.
76. PO D O S P IIE N IA .
Char. Frustules wedge-shaped, never constricted. Stipes wane,
or very short.
Derivation. From irovs, a foot, and crjxyv, a wedge.
This genus difiers from Gomphonema in the absence of a
regular and branched stipes. In their young condition the
frustules are attached in the same manner as those of the
Lxüarioe.
1 . P O D O S P H E N IA ? OCULATUM.
P late C. Fig. 9.
Char. Frustules large, Zra front view wedge-shaped ; laterally
ovoid, striated. Striæ short.
Gomphonema oculatum Kiitzing, in Linnæa, p. 568. f. 45.
G. rotundatum Ehr., xviii. f. 7.
Hab. By the side of a rapid stream, parasitic on Lyngbya
zonata, at Corham, near Bristol: Mr. Thwaites.
A very beautiful species, for an examination of which in a
recent state I am indebted to Mr. Thwaites, its first and
only discoverer In this country.
B. Frustules semi-elliptical.
77. COCCONEMA.
Char. Frustules stipitate, semi-elliptical, with a longitudinal
furi'ow, striated.
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