truncated extremities ; V. linear-acute ; striæ obscure. Length of
frustule -0033" to -0058". v.v.
Navicula curvula, Ehr. Inf. xiii. 14 ? Kiitz. Bacill. iv. 31 ? Nitzschia Sigma-
tella, Greg. Mic. Journ. vol. 3. pl. iv. 2.
Fresh water. Foole Bay, Sept. 1854 ; New Forest, Hampshire, Sept. 1854 ;
Lough Avaul, Co. Cork, June 1855, W. Sm. Elchies, Bamffshire, Aug. 1854,
Dr. Gregory.
Almost identical in form with N. Sigma, but distinguished from that species
by its far more delicate striæ and freshwater habitat.
32. Amphiprora elegans, n. sp. F. straight ; F. V. lanceolate, constriction
very slight ; V. lanceolate ; striæ 40 in -OOl". Length of
frustule -0088" to -0124". v.v.
Marine. Harwich, July 1853, Mr. Bleakeley. Milford Haven, March
1854, Mr. Roper. Salt Pans, Hampshire, Sept. 1854 ; Cork Harbour, June
1855, &c., W.Sm.
Distinguished from A. vitrea by its longer and, comparatively, more lanceolate
aud slender frustule and closer striæ.
33. Amphipleura inflexa, Bréb. Frustule arcuate, linear, slightly
attenuated towards the rounded extremities ; striæ 52 in -001". v.s.
Bréb. in Kütz. Sp. Alg. p. 88. ad specimina authentica quæ misit cl. collector.
Marine. Ilfracombe, Mr. Ralfs ; communicated by M. De Brébisson.
(Coast of Normandy, M. De Brébisson.)
34. Navicula rhomboid.es, Ehr.
Var. ¡}. V. elliptical-lauceolate ; extremities rounded, v.v.
Fresh water : frequent with Var. a. New Forest, Hampshire, Sept. 1854,
W.Sm. Near Lancaster, Aug. 1853, Mr. Ben Lomond, Sept.
1854, Dr. Arnott. Elchies, Bamffshire, Aug. 1854, Dr. Gregory.
35. Navicula firma, KiXtz.
Var. y. Extremities cuneate. v.s.
Navicula amphigomphus, Ehr. in Kütz. Bacill. xxviii. 40. et Nav. microstoma,
Kütz. Sp. Alg. p. 71. ad specim. quæ misit am. De Brébisson.
Fresh water. Lough Leven, Aug. 1854, Dr. Gregory.
The semblance of a marginal band in this, and some allied forms, appears
to arise from the beuding inwards of the edges of the valves towards the line
of suture.
36. Navicula pygmæa, Kütz. V. elliptical-oblong, subacute. Length
•0012". Breadth of V . -0005". v.v.
Kütz. Sp. Alg. p. 77. ad specim. quæ dedit cl. De Brébisson.
Brackish water. Itford, Sussex, Nov. 1853 ; Cork Harbour, Nov. 1855,
W. Sm. Coast of Norfolk, Mr. Bleakeley and Mr. Bridgman.
Differs from N. minutula, Synop. vol. i. xxxi. 274, only in the greater comparative
length and subacuteness of valve : that species must therefore yield
place to the present, and be described in future as N. pygmcea var. /3.
37- Navicula Scutelloides, W. Sm. Valve nearly orbicular ; striæ
moniliform, 18 in -OOl". Length of F. •0007". Breadth of V.
•0006". v.v.
~W. Sm. in Greg. Mic. Journ. vol. iv. p. 4. pl. i. 15.
Fresh water. Ormesby, Norfolk, Sept. 1853, Mr. Bridgman.
Rosthern
Mere, Cheshire, Sept. 1855, Dr. Arnott. Cantyre Feat, &c.
38. Navicula Bacillum, Ehr. V. linear, extremities rounded ; striæ
54 in -OOl". Length of F. -OOll" to -0022". Breadth of V.
•0005". v.s.
Ehr. in Kütz. Bacill. xxviii. 69. ad specim. authen. quæ dedit am. De Bre'bisson.
Nav. bacillaris, Greg. Mic. Journ. vol. 4. pl. i. 24.
Fresh water. Dundee, Dec. 1855, Dr. Gregory.
39. Navicula lævissima, Kütz. V. linear, or slightly inflated at
centre ; extremities truncate ; striæ 48 in -OOl". Length of valve
•0008" to -0019". Breadth of valve -00025" to -0005". v.v.
Kütz. Bacill. xxi. 14. Stauroneis rectangularis, Greg. Mic. Journ. vol. 2.
pl. iv. 17.
Freshwater: frequent. Lewes, March 1853 and April 1854; Glengariff,
Co. Cork, June 1855, &c., W. Sm. Lough End near Edinburgh, March
1854, Dr. Gregory. Bridge of Allan, Dr. Arnott. Ulverstone, Dec. 1854,
Miss Hodgson.
There is no true stauros in this species : a sufficient defining power with
accurate illumination shows that the striæ extend over the entire surface of
the valve not occupied by the nodules and median line.
40. Navicula pectinalis, Hréé. F. V. extremities truncate; V. linear