ordinary forms, which include many others intermediate in size and
outline. Conjugation and the formation of sporangial frustules
have been observed by Mr. Thwaites and myself in one species of
Himantidium.
Se c t . I. Frustules forming a lengthened filament.
1. Himantidium pectinale, Aiite. Frustules on F. V. rectangular,
straight ; V. arcuate, linear, suddenly attenuated towards the extremities,
which are slightly produced; striæ 27 in -001". Connecting
membrane obscurely striated ; striæ 48 in -001". Length
of frustule -0007" to -0058". Breadth of valve •0004". v.v.
Kütz. Bacill. xvi. 11. ad sp. authen. quæ dedit am. De Brébisson. Raben.
Süssw. Diat. 1. I . e . Conferva pectinalis. Dill. Conf. pi. xxiv. ad
specim. authen. in herb. Grev. Fragilaria pectinalis, Ag. Syst. p. 7.
Ag. Consp. p. 62. Lyng. Tent. Ixiii. D. ? English Botany, pi. 1611 ?
Grev. B. F. p. 403. Harv. Man. p. 197. Ralfs, Ann. xii. 2. fig. 3 C.
, ad specim. authen. in herb. Jenn. Hass. Alg. xcv. 1 & 2 6. Quek.
H. C. xii. 15. In conj. Thw. Ann. vol. xx. pi. xxii. A. Eunotia depressa,
Kütz. Bacill. xxix. 39 & xxx. 2. Himantidium minus, Kiitz.
Bacill. xvi. 10. ad specim. authen. quæ dedit am. De Brébisson. Conferva
lucens, Thore, et C. hronehialis, Roth., ad specim. authen. q. d. cl.
Dr. Arnott.
Fresh water. Wareham, Mar. 1848. Cook’s Bridge, Sussex, Jan. 1853,
W. Sm. Tunbridge Wells, Oct. 1844, Mr. Jenner. Woodhead, Cheshire,
May 1852, Mr. T. Brittain. Aberdeenshire, Dr. Dickie. Cader Idris, Mr.
Capron. Dolgelly Earth, Lough Mourne, and Lough Island Reavey and
Mull Deposits. (Falaise, M. Be Brébisson. Pic de Sancy, Auvergne, elev.
6000 feet, June 1854, W. Sm.)
Plate XXXII. 280.
2. Himantidium undulatum, W. Sm. V. arcuate, constricted near
the extremities, with a central inflation on the concave surface,
and one or more dorsal elevations ; striæ 22 in -001". Length of
frustule -0021" to '0058". Breadth of V. -0002". v.v.
Fragilaria pectinalis, var. /3. undulatum, Ralfs, Ann. vol. xii. pi. ii. fig. 3 d.
Hass. Alg. xcv. 2 d. Eunotia nodosa, Ehr. Microg. passim.
Fresh water. Maam, Galway, July 1853. Lough Avaul, Co. Cork,
June 1855, W. Sm. Sussex, Mr. Jenner. Newcastle, Co. Down, Mr. TV.
Thompson. Island of Arran, Br. Arnott. Quenmore, Lancashire, Mr. Johnson.
Haverfordwest, April 1854, Mr. Phillips. Lough Island Reavey and Mull
Deposits, Dolgelly Earth, &c.
Plate XXXIII. 281, varieties 281 a, a', and a 2.
3 H im a n t i d i u m So le iro lii, Kütz. V. linear, arcuate, extremities
'rounded; striæ 30 in -001". Length of F. -0005" to. -0042".
Breadth of V. -0003". v.v.
Kûtz Bacill. xvi. 9. ad specim. authen. quæ dedit. cl. De Brébisson. Raben.
Süssw. Diat. 1.3. Fragilaria pectinalis, var., Ralfs, Ann. vol. xii. pi. ii. 3.
Hass. Alg. xcv. 3.
Fresh water. Wareham, Dorsetshire, Mar. 1848, W. Sm. In Scotland,
communicated by Mr. R. Beck. Tunbridge Wells, Dec. 1842, Mr. Jenner.
(Falaise, M. Be Brébisson.)
This species so frequently occurs with internal cells, forming a variety
similar to the one noted in Meridion, that Professor Kützing has included
this peculiarity in his specific description. There is no doubt, however, of its
being merely an accidental modification of cell-growth, as we frequently find
in the same filament cells thus formed, and others following the normal mode
of self-division.
Plate XXXIII. 282. and PI. XXXV. 2 8 2 /.
S ec t . II. Frustules rarely united into a filament.
4 . Himantidium A r cu s, W. Sm. F. V. frequently arcuate ; valve
arcuate, linear, or with dorsum slightly elevated, constricted towards
the rounded extremities. Striæ 42 in -001". Length of frustule
. -0012" to -0024". v.v.
Kiitz. Bacill. xxix. 43. ad specim. authen. quæ dedit cl. De Brébisson.
Raben. Süssw. Diat. 1. 6. Eunotia Arcus, Ehr. Inf. xxi. 22 ? Fragilaria
is, in conj. Thw. Ann. vol. 20. xxii. A.
Fresh water. Wareham, Sept. 1848 and Sept. 1851. Rackham, Sussex,
Aug. 1853, W. Sm. Dolgelly Earth, Peterhead and Mull Deposits.
Plate XXXIII. 283. Suppl. PI. LX. 283.
5. Himantidium bidens, Ehr. Valve arcuate, dorsum with two
elevations constricted towards the truncate extremities. Striæ 27
in -001". Length of frustule -0024" to -0031". Breadth of V.
•0007". v.s.
Kütz. Sp. Alg. p. 9. Eunotia bigilba, Kütz. Sp. Alg. p. 6 ? Greg. M. J.
vol. 2. iv. 3.
Fresh water. Lough Island Reavey Deposit. Dolgelly Earth. Mull
Deposit.
Plate XXXIII. 284.