slightly produced ; V. scarcely siliceous ; striæ 64 in -001". Length
■0008" to -0016". v.v.
Brackish water. Iford, Sussex, Sept. 1852, JF. Sm.
Supp. Plate XXX. 251.
5. Amphora? tenera, W. Sm. F. V. ohlong, extremities round or
truncate ; V. scarcely siliceous, longitudinally rugose ; striæ 62 in
•001". Length -0015" to -0025". v.v.
Amjihora lineolata, Kiitz. Bacill. v. 36. ad specim. authen. quæ communicavit
cl. De Brebisson.
Marine. Forms a thin pellicle on stones, &c. Seaford, May 1850. Lancing,
Nov. 1852, W. Sm.
Supp. Plate XXX. fig. 252.
6. Amphora membranacea, n. sp. F. V. elliptical, with rounded
extremities ; V. scarcely siliceous, with a central transverse band ;
striæ very faint, 80 in -001". Length -0013" to •0030". v.v.
Brackish water. Poole Bay, Sept. 1848. Sussex, Sept. 1850, TF. Sm.
Near Belfast, D>\ Dickie. Near Harwich, Mr. Brightwell.
Plate II. 29.
7. Amphora? costata, n.sp. V. longitudinally costate, costæ marked
with a double line of moniliform puncta ; extremities produced.
Length -0020" to -0027". v.s.
Marine. Poole Bay, Sept. 1851, TF. Sm.
Supp. Plate XXX. 253.
8. Amphora minutissima, n.sp. F. V. elliptical or oval ; V. marked
with a transverse band ; striæ 64 in -OOl". v.v.
Freshwater. BaTs.sitic on Nitzschiasigmoidea. Near Lewes, Dec. 1850 and
Oct. 1852, TF. Sm. In ponds near London, parasitic on Nitzschia linearis,
Mr. Shadholt, Mar. 1851.
Plate II. 30.
G e n d s 5 . COCCONEIS, Ehr.
Frustules adherent, disciform ; valves elliptical, plane, with a median
line and central nodule.
In this genus the frustules are closely adherent by the surface of
one valve to larger Algæ, and are usually detached with difficulty.
The markings of the lower are less intense than those of the upper
surface, but in other respects the valves are symmetrical, and Mr.West
informs me that he has found the absence of a central nodule in the
lower valve, as noted by some writers, by no means a constant character.
1 . Cocconeis Pedicnlus, Ehr. F. arched ; V. elliptical, somewhat
angular ; disc delicately striated ; striæ 40 in -OOl". Length -0008
to -0014". v.v.
Ehr. Inf. xxi. 11. Kiitz. Bacill. v. 9.
Freshwater. Frequently attached to Lewes, Aug
1851 ; Wareham, Sept. 1851, TF. Sm. Lough Mourne Deposit. Peterhead
Deposit, &c.
Plate III. 31. Frustules with endochrome. Frontispiece fig. XXXI.
The striæ on this species are seen by a higher power as lines, concentric
with each extremity of the valve.
2. Cocconeis Placentula, Ehr. F. plane, valve elliptical, disc
striated. Length -0011" to -0016". v.v.
Ehr. Inf. p. 194. Ehr. in Kütz. Bacill. xxviii. 13.
Freshwater: frequent. Wareham, July 1849, TF. Sm. Lough Mourne
and Peterhead Deposits. Cantyre Feat and Dolgelly Earth.
Plate III. 32.
3. Cocconeis Thwaitesii, TF. Sm. F. arched; valve constricted
towards the obtuse extremities ; median line sigmoid ; disc faintly
striated ; striæ 72 in -OOl". Length -0009" to -0013". v.v.
Cymbella flexella, Kiitz. Bacill. iv. 14. Achnanthidium flexellum, Tiréh.. in
Kiitz. Sp. Alg. p. 54. ad specim. authen. quæ communicavit cl. De
Brebisson, Jan. 1853.
Fresh water. Near Bristol, May 1848, Mr. Thivaites. Mountains in