G e n u s 43. GRAMMATOPHORA, Ehr.
Frustules oblong, adhering by their opposite and alternate, or more
rarely by their adjacent angles into a zigzag chain, annulate and
septate, definite ; septa opposite, usually more or leas curved ;
valves linear or elliptical.
The curvatures of the septa, which are very conspicuous in most
species, appear like lines of written characters on the P. V. of the
. frustule, and justify the very significant name given to the present
genus.
In some species these flexures are, however, very slightly marked ;
in others entirely absent; so that the distinctive character of the
genus must be sought for in its zigzag filament, definite frustule, and
opposite septa. One or other of these features distinguish it from
Rhabdonema, Striatella, and Tetraeyclus on the one hand, and Tabellaria
on the other ; while the annulate character of the frustule separates
it from any other form. Thirteen species of Grammatophora
are described in the ‘ Species Algarum ’ ; but many of these differ
only in their relative size and the outline of the valve. Looking at
the great diversity that may be found in G. marina and G. serpentina
in these respects, I am disposed to believe that most of the above
forms may be reduced to these very common species,
1. Grammatophora marina, Kiitz. Septa with a single curvature
near the margin of the frustule ; valve elliptical or linear-lanceolate,
occasionally linear, with slightly attenuate and capitate extremities,
striated ; striæ 44 in ' 001". Length of frustule ‘0005" to
•0051". Breadth of valve ^0002" to •0005". v.v.
Kiitz. Bacill. xvii. 24 ; Sp. Alg. p. 120. Diatoma marinum, Lyng. Tent,
ixii. A. Ag. Consp. p. 53. Ralfs, Ann. vol. 11. pl. ix. 5. Grev. B. F.
p. 405. Harv. Man. p. 201. CoM/erwa iÆHîÆ/bmis, Eng. Bot. tab. 1883.
Ag. Consp. p. 54.’ Diatoma brachyyonum, Grev. B. F. p. 406. Harv.
Man. p. 202.
Marine: very frequent. Torbay, July 1846 ; Poole Bay, July 1848 ; Coast
of Sussex, Aug. 1850 ; Cork Harbour, June 1855, &c., W. Sm. (Mediterranean
Sea near Marseilles, May 1854, W. Sm. Mauritius, Dr. Arnott.)
Plate XLII. 314.
2. Grammatophora macilenta, n. sp. Frustules often curved ;
septa as in the last species ; valve linear, slightly inflated at centre
and extremities; striæ 60 in -OOl". Length of frustule -001 i" to
•0056". Breadth of valve -00015". v.v.
Marine. Salt Pans, Hampshire, Sept. 1 8 5 4 ; Cork Harbour, July 1 8 5 5 ,
W. Sm. (The Levant ; communicated by Mr. Johnson.)
The F. V., like the valve, in this species, is always much narrower in proportion
to its length than in the last ; this arises from the less convexity of
the valves, and from the slight development of the connecting membrane.
The striæ are also far more numerous than in G. marina ; and the frustule,
especially in the larger specimens, shows a decided tendency to assume a
curved form.
Supp. Plate LXI. 3 8 2 .
3. Grammatophora serpentina, Kiitz. Septa with two or more
curvatures, andahamulous extremity; valve linear, slightly attenuate
or cuneate towards the obtuse or rounded extremities ; striæ
42 in -001". Length of frustule -0009" to -0062". Breadth of
valve -0007". v.v.
Kiitz. Bacill. xxix. 8 2 ; Sp. Alg. p. 1 2 1 . Striatella toeniæformis y, Ralfs,
Ann. vol. 1 1 . pl. ix. 5 . ft.
Marine. Torbay, July 1 8 4 6 ; Cork Harbour, Oct. 1 8 5 5 , &c., W.Sm.
Ilfracombe, March 1 8 5 2 , Mr. Balfs. The Clyde, Feb. 1 8 5 4 , Mr. Ilennedy.
(AlgoaBay; Guano fromlchahoe; Mediterranean near Marseilles,&c., IF.Sm.)
Mr. West, while engraving the present species, called my attention to the
existence of a faint median line, with occasionally distinct central and terminal
nodules, in both G. marina and G. serpentina : he also remarks that the striæ
in the former case are composed of markings in linear series ; while those of
G. serpentina have the striæ, made up of markings disposed in quincunx, the
resultant lines in the one being in consequence parallel, and in the other
oblique. There can be no doubt of the general accuracy of these remarks ;
but I have not been able to assure myself that these features are uniform and
constant, and therefore hesitate to adopt them as specific distinctions.
4. Grammatophora ? Balfouriana, W. Sm. Septa direct, without
curvatures, perforate ; valves linear, elliptical ; striæ 45 in -OOl".
Length of frustule -0005" to -0012". Breadth of valve -00015" to
•00025". v.s.
Diatomella Balfouriana, Grev. Ann. ser. 2 . vol. 1 5 . pl. ix. 1 0 - 1 3 .
Fresh water. Canlochlan and Glen Callater, Perthshire, Aug. 1 8 5 4 ,