elliptical, extremities rounded ; striæ 22 in -001". Length of V.
•0008" to -0016". Breadth of V. -0002". v.s.
Bréb. in lit. Oct. 1852, cijm specim.
Brackish water. Saltcoats, Feb. 1854, and Powburn, July 1854, Dr. Arnott.
41. Navícula retusa, Bréb. F. V. extremities truncate with rounded
angles; V. linear, extremities rounded ; striæ 16 i u -001". Length
of V. -0018" to -0022". Breadth of V. -0004". v.v.
Bréb. Diat. Cherb. fig. 6.
Marine. Cork Harbour, Nov. 1855, W. Sm.
42. Navicula Cocconeiformis, Greg. V. elliptical; extremities
subacute, or slightly produced and rounded ; striæ indistinct, 54
in -001". Length of V. -0008" to -OOll". Breadth of V.
•0004". v.s.
Grev. Ann. 2nd ser. vol. 15. pl. ix. 6. Greg. Mic. Journ. vol. 4. pl. i. 22.
Fresh water. Braemar, August 1854, Dr. Balfour.
43. Navicula elliptica, K ü tz .= N . ovalis, Synop. xvii. 153.
Var. ft. Valve linear, or slightly constricted at centre, v.s.
Fresh water. Lough Leven, June 1855, Dr. Gregory.
The insertion of this interesting form affords me an opportunity of rectifying
the synonymy of N. elliptica and N. ovalis of the Synopsis, vol. i. p. 48.
M. He Brébisson informs me that N. elliptica, Kiitz. Bacill. xxx. 55, is a
freshwater form, first found by himself at Falaise; that it is identical with my
N. ovalis, and therefore claims priority over this latter, which must in consequence
be superseded. He suggests that the name N. ovalis should be
cancelled, and that the name N. Smithii be given to the marine species, which
I had designated N. elliptica-. I gladly accept the compliment, and shall
make the correction in a future revision of the text.
44. Navicula Amphisbaeua. Synop. xvii. 14?.
Var. y. V. extremities scarcely produced, and subacute, v.v.
Brackish water. Wisbeach, January 1854, Mr. S. Smith. Foundations of
Lleddan Bndge near Haverfordwest, July 1854, Mr. Okeden.
45. Navicula Rostellum, W. Sm. V. elliptical-oval ; extremities
produced into distinct rostra; striæ 80 in -OOl". Length of V.
•0015". Breadth of V . -0007". v.v.
Navicula apiculata, Greg. Mic. Jour. vol. 4. pl. i. 13.
Freshwater. Grasmere, August 1853, Falls of the Tummel, July
1854, Dr. Greville.
The name N. apiculata has been appropriated hy M. De Brebisson (Diat.
Cherb. fig. 5) to a marine species quite distinct from the present.
46. Navicula Hennedyii, n. sp. Valve elliptical, subacute, or rostrate
at the extremities ; marginal band of equal breadth throughout
; striæ 24 iu -001". Length of valve -0029" to -0042". Breadth
of valve '0016" to -0024". v.v.
Marine. Frith of Clyde, January 1854, Mr. Ilennedy. Poole Bay, September
18.54; Stomach of Pecten, Kinsale Bay, April 1855, W. Sm. Lyme
Regis, Dorsetshire, 8 fathoms, November 1855, Mr. Capron.
47. Navicula Lyra, Ehr. Valve elliptical, subacute or rostrate;
striæ in a marginal and tw’o central bands ; marginal band of
unequal width ; striæ 20 in -OOl". Length of valve •0036" to
•0064". Breadth of valve -0018" to -0026". v.v.
Ehr. in Kiitz. Bacill. xxviii. 55 ; Sp. Alg. p. 74.
Bréb.), sporangial? Synop. pl. xvii. 152 a*.
N. elliptica (N. Smithii,
Marine. Salt Pans, Hampshire, September 1854, W.Sm. Cumbrae, January
1854, Dr. Arnott.
The last two species are almost identical in form ; but the arrangement of
the striæ in éach is peculiar, and constant under every shape and size of the
individual frustule. In N. Hennedyii the marginal striæ form a continuous
band of equal width along the circumference of the valve, aud the unstriated
portion of the surface, between the border and the linear longitudinal bands
that lie along the median line, is, in consequence, of unequal width, having the
outline of a segment of a circle. The unstriated portion of N. Lyra is, on
the contrary, almost linear, and the marginal band of striæ has the outline of
a segment of a circle slightly inflated at the centre of its base : iu both the
striæ are beautifully mouiliform, though the character is more apparent in the
last : both species occur with the extremities sometimes subacute and sometimes
rostrate.
48. Navicula humerosa, Bréb. Valve nearly linear, or slightly