466 Mr. J. Ralfs on the British species 0/ Gomphonema. 



Very minute, brown; frustules cuneate, curved, often nearly ses- 

 sile ; sometimes, especially in the maritime variety, on an elongated 

 brand 'ed stipes, generally binate, though occasionally as many 

 as four frustules are united together. Terminal puncta large ; 

 each of the puncta at the base, which are more evident than in 

 the other species, is connected with the upper punctum on the 

 same side by a line passing dovra the frustvile. A slight notch 

 or pimctum is present at the centre of the concave but not of the 

 convex margin; lateral sm-faces very narrow, generally clavate, 

 striated. 



This species differs from all the foregoing in its curved frus- 

 tules, in havmg a notch on one only of the lateral margins, and 

 two striae passing down the frustule and connecting the upper 

 and lower puncta. 



I have attempted in vain to find some specific character to di- 

 stingTiish the maritime form. It is more branched, has a very 

 rigid appearance, looking indeed not unhke a zoophyte, and the 

 strise connecting the puncta on the front surface are strongly 

 marked ; but intermediate specimens are occasionally met with 

 in which all these differences vanish. 



Plate XVIII. fig. 9, Gomphonema minutiss'imum, 



8. G. paradoxum, Ag. Frustules broadly cuneate, puncta at the 



upper end strongly marked, with a stria from each passing down 



the frustule ; lateral surfaces clavate, narrow, not striated. Ag. 



Consp. Diatom, p. 34 ; Harv. Br. Alg. p. 208 ; Kutz. Syn. Diatom. 



p. 569. Echinella paradoxa, Grev. Crypt. Fl. t. 25 ; Eh. Die Infus. 



p. 221 ; Pritch. Infus. p. 208. 



On marine algse very common. 



This species forms a brow^i gelatinous covering on the smaller 

 algse ; it turns green in di-ying. At fii-st the frustides are nearly 

 sessile, but when matm'e they are attached to a more or less 

 branched stipes forming a fringe on the infected plant, which is 

 distinctly visible to the naked eye ; the frustules are broadly cu- 

 neate, mth two conspicuous puncta at the upper end, and two 

 stride extend the entire length of the frustule. There are no 

 puncta on the lateral margins ; the lateral sm-faces are very nar- 

 row in comparison with the front, much more so in fact than in 

 any of the preceding species ; they are clavate in form and not 

 striated. 



I am not sufficiently acquainted ^"ith Gomph. majusculum, 

 Harv., to make any remarks upon it. 



Plate XVIII. fig. 10. Gompho7iema paradoxum. 



Analysis. 



{Lateral surfaces of the frustules constricted beneath the 

 apex so as to appear urn-sliaped 2 

 Lateral surfaces not urn-shaped 4 



