Fresh water. Near Guildford, Mr. Capron, Nov. 1852. Lough Mourne
Deposit. Cantyre Peat. Premnay Peat. (New Zealand ; Nova Scotia.)
Plate XIX. 187. Frustide with endochrome. Frontispiece, fig. CLXXXVII.
4. Stauroneis salina, n. sp. V. elliptical-lanceolate ; stauros linear ;
striæ faint, 45 in -001". Length -0016" to -0022". v.v.
Marine. Shoreham, Aug. 1851, IF. Sm. Folkestone, Nov. 1852,Mr. Capron.
Plate XIX. 188.
5. Stauroneis dilatata, n. sp. V. elliptical, extremities slightly
produced ; stauros linear, not reaching the margin ; striæ 30 in
•001". v.s.
Fresh water. Aberdeenshire, Dr. Dickie. Cantyre Peat.
Plate XIX. 191.
6. Stauroneis cnicicula, n. sp. V. elliptical, extremities slightly
produced ; stauros very narrow, linear, reaching the margin, v.v.
Marine. Belfast Bay, Aug. 1849, IF. Sm.
Plate XIX. 192.
7. Stauroneis anceps, Ehr. V. elliptical, constricted towards the
produced extremities; stauros linear, not reaching the margin;
striæ very dehcate, 45 in •001". v.v.
Ehr. in Kiitz. Bacill. xxix. 4 ?
Fresh water. Swanage, Dorset, March 1849 ; Lewes, Oct. 1852, IF. Sm.
Lanshaw Spa, Katefield, Lancashire, Mr. G. Smith, Jan. 1852. Ben M' Dhui,
Mr. P. Grant. Marl, Co. Down.
Plate XIX. 190.
8. Stauroneis linearis, Ehr. V. elliptical, inflated at centre and at
the extremities, which are apiculated ; stauros linear, reaching the
margin; striæ obscure, v.v.
Kiitz. Bacill. XXX. 26.
Fresh water. Plumpton and Lewes, Sussex, Apr. 1852, IF. Sm. Shalford,
Mr. Capron. Premnay Peat.
9. Stauroneis punctata, Kütz. V. elliptical, extremities produced;
stauros linear, central ; striæ radiate, punctate, 27 in -001". v.s.
Kütz. Bacill. xxi. 9.
Fresh water. Lough Mourne and Peterhead Deposits. Premnay Peat.
Ben M” Dhm, Mr. P. Grant. Cantyre Peat. (San Fiore, Italy.)
Plate XIX. 189.
10. Stauroneis pulchella, n. sp. F. V. oblong, constricted at the
centre; V. elliptical; stauros central, dilated towards the margin;
striæ very distinct, 30 in -001", punctate; puncta hexagonal!
Length -0048" to •0096". v.v.
fi. Dry valve purplish, somewhat acuminate.
Marme. Coast of Sussex, Aug. 1850, and Poole Bay, Sept. 1851, IF Sm
I 1846 Coast of Sussex, Aug. 1860, W. Sm. Near Ipswich,
Mt. Hodgson, Nag. IS51. Harvndh, Mr. Shadbolt. (Peruvian Guano.)
Plate XIX. 194. b. outline of F. V. Var. fi. PI. XIX. 194 fi.
G e n u s 2 2 . PLEUROSIGMA, W. Sm.
Frustules free, elongated; valves convex, sigmoid, with a central longitudinal
hne, and nodules at centre and extremities, striated;
striæ resolvable into dots, which are frequently hexagonal.
The sigmoid form of the valve more or less present in all our native
species, at once distinguishes this genus from its allies; but even in
the absence of this feature, which I have noticed to be wanting in at
least one species, discovered by M. De Brebisson, on the coast of
Normandy, the structure of the siliceous valve retains its characteristic
peculiarities. The striæ are invariably so closely arranged, that
their discovery and resolution are among the most difficult operations
m microscopy. Their true character has been, in consequence, frequently
mistaken ; some observers having considered these appearances
of stnæ to arise from series of perforations, and others from
rows of beads, or minute elevations. With the latter I have been
disposed to coincide, until, aided by the careful manipulation and
exceUeut object-glasses of Mr. Richard Beck, who has shown me
the hexagonal outline of these supposed beads, I have been led to