acute. Length of frond 1". Length of frustule ’0009". Breadth
of valve -00015". v.s.
Marine. Tor Abbe_y Rocks, April 1842, M ra . Griffiths.
Plate LIX. 372.
G e n u s 57- HOMOEOCLADIA, Ag.
Frond filiform, sparingly divided ; frustules nitzschoid, usuallj' somewhat
fasciculated ; striæ obscure.
The structure of the frustules, which is that of the genus Nitzschia,
separates the present from the other genera of the tribe. The species
are all marine, and appear to be rare, as few British localities are
known to me, or have been given by former authors.
1. Homoeocladia Martiana, Ag. Frond simple, or dichotomously
divided, rugose; height of frond -.3" to '7"; frustules usually in
dense fascicles, on F. V. linear-lanceolate, obtuse; V. linear, obtuse.
Length of frustule -0120". Breadth of valve -0002". v.s.
Ag. Consp. p. 25. ad sp. authen. in herb. Grev. Kiitz. Bacill. xxx. 83. Sp.
Alg. 98. Prit. Anim. xvii. 47-49. Homoeocladia Anglica, Ae. Consp.
p. 25. Kütz. Bacill. xxx. 82. Ralfs, Ann. 1st ser. vol. ffi. iii. 1.
“ Wrongly described in the ‘Annals’ as H. Anglica,” cl. Ralfs, m lit.
Nov. 1852.
Marine. Torquay, Mrs. Griffiths. Ilfracombe, Sept. and Oct. 1844, Mr.
Ralfs. (Coast of Normandy, Si. Be Brébisson.)
A rare form, which has been described, as will be seen above, under the
two designations of Anglica and Martiana ; the specimens wliich I have seen
thus variously marked all belong to one species, and I have Mr. Ralfs’ authority
for referring his H. Anglica to the older designation of Agardh.
Plate LV. 347.
2. Homoeocladia filiformis, n. sp. Frond linear, simple; fascicles
containing three or four frustules ; height of frond -2" to -3" ; F. V.
linear-lanceolate, obtuse; V. linear-lanceolate, somewhat acute.
Length of frustule -0043". Breadth of V. -0003". v.v.
/3. A smaller form. Length of frustule-OOiS". Breadth of V .-0002". v.v.
Brackish water. Bexhill, Sussex, Sept. 1850 ; ¡3. Near Lewes, Aug. 1852
W. Sm. ' ’
Plate LV. 348. Var. ¡3. Plate LV. 348 ¡3.
3. Homoeocladia sigmoidea, n. sp. Frond linear, simple; frustules
irregularly fasciculated in bundles of about six ; F. V. sigmoid;
V. linear, attenuated towards the extremities. Height of frond
■3" t o -6". Length of frustule-0025". Breadth of valve-0002". v.v.
Brackish water: attached to grass. Near Wareham, Dorset, Jan. 1850, IF. Sm.
Plate LV. 349.
S u p p l . G e n u s 58. ASTERIOWELLA, Hass.
Frustules linear, inflated towards one or both extremities ; adhering
by their adjacent angles into a star-like filament.
The present genus, first constituted by Mr. Plassall in his pamphlet
“ Microscopic Examination of the Water supplied to the Inhabitants
of London,” was not known to me when I arranged the genera of the
present work. I t ought probably to be placed next after Diatoma,
as it agrees with that genus in the general form of its frustules, differing
from it chiefly iu the mode of adherence which takes place after
self-division.
The species which have reached me through the kindness of the
correspondents mentioned below were none of them in a satisfactory
condition for examination, and it would require a further acquaintance
with them in a fresh state to clear up several points in their
habit and structure.
1. Asterionella formosa, Hass. Star of from four to eight frustules
; on F. V. somewhat more enlarged at the base (point of
adherence) than at the summit. Length of frustule -0021" to
•0031". v.s.
Hass. I. c. p. 10, &c.
Fresh water; in water supplied to the town of Tenby, March 1853, Mr.
Roper. Rosthern Mere, Cheshire, Sept. 1855, Dr. Arnott.
2. Asterionella Ralfsii, W. Sm. Frustules on F. V. exactly linear ;
valve attenuated towards one extremity, constricted towards the
other, w'hich is rounded and capitate ; striæ obscure. Length of
frustule -0018". v.s.
Diatoma stellare, Ralfs, MSS. ad specim. iu Herb. Jenn.
VO L. I I . „