G e n ü s 28. RHIPIDOPHORA, Kütz.
Frustules stipitate, cuneate ; valves convex, obovate, inflected at larger
e.xtremity, traversed by a median line.
1. Rhipidophora paradoxa, Kiitz. Stipes dichotomous ; frustules
on F. V. obovate, rounded at the upper extremity; V. rounded at
upper, acute at lower extremity, occasionally faintly striated.
Length -0016" to -0025". v.v.
Kiitz. Bacill. X. 5. Echinellaparadoxa, Lyng. Tent. Ixx. fig. E. Gomphonema
paradoxum, Ag. Consp. p. 34. ad specim. quæ communicavit cl.
Dr. Greville. Ralfs, Ann. vol . xii. pi. .xviii. 10.
Marine; frequent. Jersey, Aug. 1852, Sm. Penzance, 3Ir. Ralfs.
Aberdeen, Dr. Dickie. Frith of Forth, Dr. Greville.
Plate XXV. 231.
2. Rhipidophora elongata, Kiitz. Stipes dichotomous ; F.V. nearly
linear, truncate ; V. somewhat acute ; striæ obscure. Length -0032"
to -0042". v.s.
Kiitz. Bacill. X . 6? Gomphonema tinctum, Ag. Consp. p. 35. ad specimina
quæ communicavit cl. Dr. Greville.
Mai-ine. Frith of Forth, Dr. Greville, 1849. Cromarty, Mr. Johnson.
Plate XXV. 232.
3. Rhipidophora Dalmatica, Kütz. Stipes incrassated, irregularly
branched; F.V. truncate; V. very narrow, somewhat acute; striæ
obscure. Length -0008" to -0016". v.v.
Kütz. Bacill. ix. 7 ?
Marine. Hastings and Beachy Head, Sussex, July 1850, W. Sm.
Plate XXV. 230.
G e n u s 29. LICMOPHORA, Ag.
Frustules mneate, stipitate; stipes incrassate, irregularly branched;
valves convex, elongated, inflected at larger extremity, and traversed
by a longitudinal median line.
The frustules of the present genus differ in no essential respect
from those of Rhipidophora. They are, it is true, longer and narrower,
and probably less firmly siliceous; but none of these circumstances
seem to be of generic importance. The separation of the genera must
therefore rest upon the fan-like arrangement of the frustules, upon
the summit of an incrassate and irregularly dichotomous pedicel,
which occurs in Ucmophora. This character is however of more importance
than might at first view appear, as it indicates a peculiarity
in the self-dividing process. In Rhipidophora paradoxa and elongata,
self-division is immediately foUowed by the separation of the half-new
frustules and a dichotomy in the filamentous stipes; while in the present
genus the frustules remain for some time coherent, and continue
dividing and multiplying on the summit of the pedicel, which becomes
elongated and incrassated at each successive repetition of the process.
A branching, or rather longitudinal rupture of the pedicel takes
place at irregular intervals, and the entire plant presents us with
more or less complete flabella on the summit of the branches, and
imperfect flabella or single frustules irregularly scattered throughout
the entire length of the pedicel. Rhipidophora Dalmatica possesses
the same character to a certain extent; but the flabella are much
less perfect than in the present genus, while its pedicel is occasionally
so abbreviated as to ally it to Podosphenia.
I have given, in accordance with the authority of my predecessors,
two species of the present genus; hut I am far from satisfied that
they are truly distinct; and I am disposed to believe that a wider
comparison of specimens will necessitate their union. The fronds
of both are parasitic upon the larger marine Algai, upon Zostera
marina, and upon various species of Zoophytes.
]. Licmophora splendida, Grev. F.V. nearly linear, frequently
attenuate, and rounded at the upper extremity; V. imperfectly