the genera which have preceded it, and the presence of nodules in
Its valves from Podosphenia and Phipidophora, with which the present
genus has sometimes been confounded. The latter genera are
also exclusively marine, while the species of Gomphonema, with one
exception (and that a species doubtfully connected with the present
genus), are all inhabitants of freshwater streams and ponds. The
same mode of branching characterizes the stipes of the present genus
as that noticed under the genus Cocconema ; and excluding the exceptional
species just mentioned, this appendage, in the present as in that
genus, when fully developed, consists of an elongated dichotomous
filament. Conjugation and the formation of Sporangia have been
observed by Mr. Thwaites in G. Berkeleyi, G. tenellum, and G. curva-
tum-, and by myself in those species, G. capitatum and G. marinum.
1. Gomphonema geminatum, Ag. F. V. slightly cuneate, truncate ;
V. inflated at the centre and constricted towards each extremity,
of which the one more distant from the stipes (the upper) is enlarged
and rounded; striæ moniliform, 24 in -001". Length -0041" to
■0052". v.v.
Ag. Syst. p. 12. Grev. C. F. pi. 244. fig. 2. Harv. Man. p. 207. Ralfs
Ann. vol. XU. pi. xviii. 3. Hass. Alg. xcviii. 1. Kutz. Bacill. xiii. 2.
Eohmellageminata,UjTi^.'Teat.\s.s..-D. Gomp. ampullacemn, Gre-i B F
p. 410. ex specim. authen. quæ communicavit cl. Dr. Greville.
Fresh water: subalpine streams, not uncommon. Pentland Hills, Dr
GretdN Lolgelly, Mr. Rafs. Wray, Lancashire, Mr. G. Smith. Ben
T o s if^D Îrily Earth. Lough Mourne De-
Plate XXVII. 235. Frustules with endochrome, Frontispiece, fig. CCXXXV.
2. Gomphonema constrictum, Mr. F .V . distinctly cuneate; upper
extremity rounded, lower obtuse ; V. more or less constricted towards
the upper extremity, attenuated below; striæ 27 in -OOl".
Length -0012" to -0024". v.v.
Kütz Bacill, xiii 4 Gomp. truncatum, Ehr. Inf. xviii. 1. Hass. Alg. xcviii. 2
S'ek ■ Pl- 4- Gomp. geminatum,
!'™®f-Mayl850,&c.,HA,S™. Harrison’s Rocks,
gelly Eartir Mourne Deposit. Peterhead Deposit. Dol-
3. Gomphonema acuminatum, Ehr. F. V. cuneate, slightly inflated
at centre, and crested at the upper extremity ; V. constricted
triangular and apiculate above, attenuated below ; striæ 24 in -OOl".
Length -0011" to -0028". v.v.
¡3. V. much elongated and slightly constricted below. Length '0031" to
y. V. cuneate at larger extremity, constriction often obsolete.
Ehr. Inf. xviii. 4. Kûtz. Bacill. xiii. 3. ad specim. qnæ dedit amic. De Brebisson.
Prit. Anim. xvi. 23. Hass. Alg. xcix. 1. Gomp. minutum,
Ralfs, Ann. vol. xii. pi. xviii. 5.
Var. (3. Gomp. coronatum, Kütz. Bacill. xxi. 12.
Fresh water : frequent. Lewes, Nov. 1851, IF. iSm. Lough Mourne and
Peterhead Deposits. Var. ¡3. Dolgelly Earth. Rescobie, Mr. P. Grant.
Var.y. LeweSjEeb. 1853, &c. IF. Sm. (San Fiore, Italy. Little Falls, New York.)
Plate XXVIII. 238. a, a!, & b. Var. ¡3. 238 [3. Var. y. 238 a" & a'".
4. Gomphonema cristatum, Ralfs. F. V. obovate, crested ; V. ob-
ovate, apiculate ; lower extremity acute ; striæ 24 in ’OOl". Length
•0009" to -0022". v.v.
Ralfs, Ann. vol. xii. pi. xviii. 6. Hass. Alg. c. 1. Gomp. Augur, Kütz. Bacill.
xxix. 74?
Fresh water. Shoreham, Kent, Dec. 1842 ; Farnham, Surrey, Jan. 1844,
Mr. Jenner. Pond, St. James’s Park, Loudon, Jan. 1852, Mr. Shadbolt.
Plate XXVIII.
239. Frustules with endochrome. Frontispiece,
fig. CCXXXIX.
5. Gomphonema dichotomnm, Kütz. F.V. slightly cuneate, truncated
; V. lanceolate, acute; striæ 34 in -001". Length -OOll" to
•0018". v.v.
ß. Stipes incrassate ; frustules flabellate, obtuse.
Ralfs, Aim. vol. xii. pi. xviii. 7- Kiitz. Bacill. viii. 14. Hass. Alg. xcix. 2.
Gomp. minutum, Ag. Consp. p. 34. ex specim. authen. quæ communicavit
cl. Dr. Greville. Gomp. gracile, Elir. Inf. xviii. 3.
Fresh water. V’areham, Jan. 1850. Penzance, 3Ir. Ralfs. Marl, Co.
Down. Premnay Peat. Var. ß. Plumpton, Sussex, Apr. 1852, IF_
Plate XXVIII. 240. Var. ß. 240 ß. Frustules with endochrome. Frontispiece,
fig. CCXL.