what setaceous and robust ; and the second including those species
whose frustules are imperfectly siliceous, and whose fronds are flaccid
and deUcate in character; and while I give the size and form of the
frond, generally characteristic of each species, I rely mainly for their
discrimination upon the shape, size and striation of the individual
frustules.
In the nomenclature of my species, I have mainly followed Harvey’s
‘ Manual of the British Algæ,’ because the genus is there more fully
described than in any other English work, and because I have been
enabled by the kindness of Mrs. Griffiths to examine authentic specimens
of most of the species adopted by Dr. Harvey. To attempt to
reduce these species to those of Kützing’s, without specimens of the
latter, and guided alone by the descriptions and figures in the ‘ Species
Algarum’ and ‘ Bacillai-ien,’ would be to introduce further perplexity
into a synonymy already sufficiently confused.
S e c t . I. Erustules firmly siliceous : frond usually setaceous.
1. Schizonema cruciger, n. sp. Frond filiform ; filaments implicate
below, free above, much divided; frustules crowded; valves
with a distinct stauros, lanceolate, acute; striæ distinct, 40 in
•001". Length of frond -l" to 1-2". Length of frustule -0033" to
•0051". v.v.
Marine: on krger Algæ. Hove, Sussex, March 1851; Hastings, May
18o2, &c., TV. Sm. Hull, Mr. B. Harnson. Cumbrae, Feb. 1864, Mr. R.
'Kennedy.
Plate LVI. 354. Plate LVII. 356.
2. Schizonema helmintosum, Cham. Frond filiform, or by cohesion
irregularly submembranous, much and irregularly divided;
ultimate divisions short, abrupt ; frustules in single files or crowded ;
valves elliptical ; striæ 48 in -001". Length of frond -5" to 2".
Length of frustule -0014" to -0019". v.v.
a 2 n ^ " ‘‘ ^ P- 210- “‘i
Marine : on rocks. Tovhay, Mrs. Griffiths. Aberdeen, Hr. Poole
1? -b Nri, frequent, W. Sm. Isle of Arran, Aug.
18o3; Fnth of Clyde, March 1854, Dr. Arnott. Exmouth, Miss Cutler.
The valves are often somewhat acute, and not with rounded apices as in the
figure.
Plate LVI. 355.
3. Schizonema comoides, Ag. Frond filiform, simple beloiv, much
divided and fasciculated above ; frustules crowded ; valves lanceolate;
striæ 48 in -001". Length of frond -5" to P5". Length of
frustule -0008" to -0013". v.v.
Ag. Consp. p. 19. Harv. Man, p. 213. ad specim. authen.
Marine : on rocks, or mud banks. Torbay, Mrs. Griffiths. Aberdeen,
Dr. Dickie. Coast of Sussex, March 1854, W. Sm.
Plate LVII. 358.
4. Schizonema confertnm, n. sp. Frond filiform, sparingly divided
throughout; frustules exceedingly crowded; valves lanceolate,
acute; striæ marginal, indistinct. Length of frond •!". Length
offrustule -0008" to -0011". v.s.
Schizonema implicatum, Harv. sic Dr. Dickie in lit.
Marine. Aberdeen, Dr. Dickie.
This is certainly not S. implicatum, Harv., the valves being different both
in form and striation.
Plate LVII. 359.
5. Schizonema mncosnm, Frond filiform, gelatinous, simple
below, by cohesion submembranous above, margin irregularly
ramulous; frustules in files, few', subdistant; valve elliptical, delicately
striated. Length of frond -2". Length of frustule -0009"
to -0013". v.v.
Kütz. Bacill. p. 115. tab. xxvi. 9.
Marine: in muddy pools. Hove, near Brighton, April 1854, W. Sm.
I cannot refer this species to any in the ‘ Manual,’ and have ventured to
adopt Kützing’s name, as my specimens coincide in most particulars with the
description and figure of S. mucosum given in the ‘ Bacillarien.’
Plate LVII. 360.
6. Schizonema Smithii, Ag. Frond filiform, robust, simple below.