fi. Synedra constricta, Kiitz. Bacill. iii. 70. ad spec, quæ dedit amie. De Bré-
bissoii.
Bracldsb water. Near Lewes, Oct. 1851, )F. Sm. Hull, Mr. Harrison.
Coast of Norfolk, Mr. Shadbolt.
Plate XIII. 112. Plate XIV. 112.
A'ar. fi. Supp. Plate XXXI. 112/3.
17. Nitzschia bilobata, W. Sm. P. on P. V. elliptical, with a central
constriction, and round or truncate extremities ; V. linear-lanceolate,
acute; puncta double; keel central; striæ distinct, 56 in
•001". Length -0033" to -0058". v.v.
Amphiprora latestriata, Bréh. in Kiitz. Sp. Alg. p. 93. sic cl. De Brebisson
in lit. Aug. 1852.
Brackish water. Poole Bay, Oct. 1849. Shoreham, Nov. 1852.
Plate XV. 113.
18. Nitzschia plana, n. sp. P. on F. V. elliptical, with a central
constriction and acute extremities ; V. linear-lanceolate, acute ;
puncta in a single row; keel eccentric; surface of V. obscurely
striated; striæ interrupted, 56 in -OOl". Length -0058" to
•0076". v.v.
Brackish water. Poole Bay, June 1849, W. Sm.
Plate XV. 114.
S e c t . VI. Valves with extremities produced. iCeratoneis, Kiitz.)
19. Nitzschia birostrata, TV. Sm. F. V. straight, in central portion
somewhat lanceolate; extremities produced into extremely
long beaks ; keel nearly central ; puncta in a single row ; striæ
obscure. Length •0128" to ‘Oieg". v.s.
Ceratoneis longissima, Kiitz. Sp. Alg. p. 891. ad specimina quæ communicavit
cl. De Brebisson, Sept. 1852.
Marine. Near Walton, Essex, Mr. Topping.
Plate XIV. 119.
20. Nitzschia Closterium, W. Sm. F. V. arcuate ; V. faintly striated;
striæ 90 in 'OOl"; otherwise as in the last. v.v.
Ceratoneis Closterium, Kiitz. Bacill. iv. 11. Ehr. in Prit. Anim. xv. 59.
Marine and brackish water. Hove, Sussex, May 1851, IF. Sm.
Plate XV. 120.
21. Nitzschia reversa, n. sp. F. V. lanceolate ; extremities produced
into beaks which are bent in contrary directions; striæ 48 in
•001" ; puncta obsolete, v.v.
Brackish water. Near Lewes, Nov. 1851, IF. Sm.
Plate XAL 121.
22. Nitzschia acicularis, W. Sm. F. V. lanceolate, extremities
produced, beaks straight; V. faintly striated; striæ 98 in -0 0 1 ".
v.v.
Synedra acicularis, Kiitz. Bacill. iv. 3.
Fresh water. Near Lewes, May 1852, IF. Sm.
Plate XV. 122.
23. Nitzschia Taenia, W. Sin. P. V. linear-lanceolate, occasionally
sigmoid, extremities produced ; beaks direct or curved ; V. striated,
striæ 72 in -OOl"; endochrome in dry frustule apparently arranged
in a spiral manner, v.v.
Ceratoneis gracilis, Bréb. in Kiitz. Sp. Alg. p. 89. ad specim. quæ communicavit
cl. De Brébisson, Oct. 1852.
Brackish water. Near Lewes, Sept. 1851, W. Sm. Brauuton, Devonshire,
Mr. Ralfs, Oct. 1849.
Plate XV. 123.
G e n u s 1 7 . AMPHIPRORA, Ehr.
Frustules free, elliptical, constricted; valves convex, keeled; keel
central, with a longitudinal line, and nodules at centre and extremities.
The very peculiar frustules of this genus cannot be confounded
with any others, save with those of the fifth section of the last genus,
and from these they are usually distinguished without much difficulty,