n,
i l
W. Sm. Ami. 2nd Ser. vol. ix. p. 10. pl. ii. 8. Prit. Anim. xx. 8.
Marine. Coast of Sussex, Nov. 1850, TT". Sm. Southampton, Mi’. /««««•.
River Orwell, near Ipswich, Mr. Hodgson. (Coast of Normandy, M. De
Brébisson.)
Plate XXII. 214.
23. Pleurosigma Hippocampus, W. Sm. V. broadly lanceolate,
obtuse, flexure considerable ; colour pale brown ; long, striæ 32 in
•001"; trans, striæ 40 in -OOl". Length -0050" to -0066". v.v.
W. Sm. Ann. 2nd Ser. vol. ix. p. 10. pL ii. 9, 10. Prit. Anim. xx. 9, 10.
Namcida Hippocampus, Ehr. Inf. xiii. 11 ? Kiitz. Bacill. iv. 29? Prit.
Anim. iii. 145.
Brackish water. "Brooks” near Lewes, Sept. 1850, TF. Sm.
Hull,
3Ir. B. Harrison. Titchwell, Norfolk, 3Ir. Brightwell, Sept. 1851.
Plate XXII. 215. Outline of young (?) specimen, 215 ¡3.
24. Pleurosigma attenuatum, TV. Sm. V. lanceolate, obtuse, flexure
moderate; colour purplish brown; long, striæ 30 in •001",
trans, striæ 40 in -OOl". Length -0075" to -0108". v.v.
\V. Sm. Ann. 2nd Ser. vol. ix. p. 11. pi. ii. II, 12 & 13. Prit. Anim. xx.
Alg,
Fresh water : frequent in streams and ditches. River Froome, Dorsetshire,
May 1849; Plumpton, Sussex, and many other places, Apr. 1851, TF. Sm.
Guildford, 3Ir. Capron. Lough Mourne Deposit. Peterhead Deposit. Cantyre
Peat.
Plate XXII. 216. Outline of F. V. in S. D. 216 rf. Outline of young (?)
specimen, 216 fi.
25. Pleurosigma lacustre, TF. Sm. V. lanceolate, acute, flexure
considerable ; colour pale brown ; long, and trans, striæ 48 in •001".
Length -0052" to •0068". v.v.
W. Sm. Ann. 2nd Ser. vol. ix. p. 12. pi. ii. 14. Prit. Anim. xx. 14.
Fresh water. Brooks and ponds near Lewes, Oct. 1851, TF. Sm.
Plate XXI. 217.
26. Pleurosigma Spencerii, TV. Sm. V. lanceolate, obtuse, flexure
slight; colour pale brown; “ trans, striæ 50 in •001", long, striæ
55 in -001".” (R. B.) Length -0033" to -0041". v.v.
W. Sm. Ann. 2nd Ser. vol. ix. p. 12. pi. ii. 15. Prit. Anim. xx. 15. Navicula
Spencerii, Quekett on the Microscope, pi. ix.
Fresh water. Near Lewes, Sept. 1850, TF. Sm. Reading, Mr. C. Poulton.
Plate XXII. 218.
G e n u s 23. SY NEDR A, Ehr.
Frustules attached, elongate, rectangular ; valves linear or lanceolate,
plane or convex.
In the present genus the frustules, though often found in a free
state, are at first invariably attached to larger Algæ, or other plants,
by a cushion-like pedicel, which, in a few cases, becomes developed
into a more or less distinct stipes. In some species the frustules,
after self-division, are speedily detached from this gelatinous cushion,
which in such cases rarely presents us with more than two or four
individuals, as in S. lunaris. In others, the frustules, after repeated
division, still remain adherent to their pedicel ; and the result is a
fan-like band of frustules, as in S. pulchella, or a stellate cluster,
as in S. radians. The valves are usually furnished with a central
pseudo-nodule and median line, the extremities of which are slightly
dilated ; but these characters are variable, and not unfrequently absent,
and are therefore inadmissible in the generic description.
S ect. I. Pseudo-nodule obsolete or very minute ; frustule arcuate.
1. Synedra lunaris, Ehr. V. narrow, linear, slightly attenuated,
obtuse; striæ 36 in •001". L e n g th -0025" to •0038". v.v.
Ehr. Inf. xvii. 4, Kütz. Bacill. xiii. i. 5. xv. 1. Prit. Anim. iv, 185. Exi-
laria lunaris, Hass. Alg. xcvii. 4.
Fresh water. Boggy pools, Dorsetshire, Dec. 1849 ; near Lewes, Nov.
1852, TF. Sm. Coldbath Spring, Tunbridge AVells, Mr. Jenner, Apr. 1842.
Lancashire, Mr. Johnson, Apr. 1852.
Plate XI. 82.
2. Synedra biceps, TV. Sm. V. linear, inflated at the obtuse extremities;
striæ 48 i n -001". L e n g th -0042" t o -0075". v.v.
Eunotia Jlexuosa, Kiitz, Sji. .Alg, p, 6. ad specim, authen, quæ misit cl,
De Brébisson, Jan, 1853,