GOMPIIONEMA. 



421 



Hah. On rocks in subalpinc streams, Scotland : Dr. Gre- 

 ville. North of Ireland : Mr. D. Moore. Near Bandon, 

 CO. Cork : Prof. G. J. Allman. On dripjiing rocks, 

 near a waterfall at Carnlough, co. Antrim: Mr. W. 

 Thompson. Rapid streams at base of Cader Idris ; 

 and in the river above Dolgelly, North Wales: Mr. 

 Rolfs. 



" This plant forms large cushion-like tufts on the rocks in 

 rapid streams. It is not in the least mucous, but is of a 

 spongy texture, being composed of densely interwoven 

 filaments. In a young state its colour is brownish, from the 

 frustules covering the surface; but as these fall off it becomes 

 whitish, and indeed not unlike a tuft of wool. Filaments 

 repeatedly dichotomous ; frustules much larger than in any of 

 the following species, simple or binate, linear cuneate, with- 

 out puncta at the upper end ; portions of the lateral surfaces 

 are frequently visible along the sides. Lateral surfaces urn- 

 shaped, broader than the front, Avith numerous transverse 

 dotted strite. There is a central longitudinal pellucid line, 

 slightly dilated at each end with a larger dilatation in the 

 centre ; the latter at first sight may be taken for a perforation, 

 Avhich it undoubtedly is not : from the central punctum the 

 stria? are somewhat radiant : the pellucid line docs not quite 

 extend to the upper end." — Ralfs. 



2. GOMPHONEMA TRUXCATUM Ehr. 



Plate XCVIII. Fig. 2. 



Char. Frustules in front view cuneate, with tioo evident puncta 

 at the upper end. Lateral surfaces urn-shaped, striated. 

 G. truncatum and G. paradoxum Ehr., Abhandl. der 

 Akademie d. AVissensch. zu Berhu, 1831, p. 88. 1833, 

 p. 319. G. pohliciforjne Kiitzing, in Linna^a, 1S33, 

 p. 569, 570. t. xvi. fig. 50. G. truncatum Ehr., Die 

 Infus. p. 216. pk xviii. fig. 1. G. suhramosum Kiitz., 

 Synops. Diatom, p. 570. fig. 44. G. pohliccforme Ealfs, 

 in Annals, vol. xii. p. 461. pi. xviii. f. 4. G. cajntatum 



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