Gomphonema.] ALGJE DIATOMACEiE. 409 



branched, branches alternate, the frustula linear wedge-shaped 

 flabelliform. — Ag. Conspect. Crit. Diat. p. 42. — Meridion radi- 

 ans, Ag. Syst. Alg. p. 3. — Exilaria fiabellata, Grev. Crypt. FL 

 t. 289. 



Parasitic on marine Alga? and Zostera marina ,• Bantry Bay, Ireland, 

 Miss Hutching. Appin, Capt. Carmichael and Rev. M. J. Berkeley. — A 

 singularly elegant species, forming dense green tufts, half an inch in 

 height; the frustula united into beautiful fan-shaped expansions at the 

 ends of the branches, and bearing a single or double row of globules, or 

 oblong spots of a darker colour than the yellow frustula themselves. 

 The finest specimens I have seen are those on Zostera mariiia. The 

 Irish ones are smaller, and grew on Chorda Filum, var. T/oix. 



106. Meridion. Ag. Meridion. 



Frustula wedge-shaped, in plane sessile circles or segments of 

 circles. — Name ; from pipe, iboi, a portion or particle, in allusion 

 to the minute fragments which compose it. 



1. M. circuldre, Ag. (circular Meridion); mucose stratum 

 scarcely any, frustula united into numerous nearly complete 

 circles. — Ag. Conspect. Crit. Diat. p. 40. — Echinella circularis, 

 Grev. Crypt. FL t. 35. — Exilaria circularis, Grev. I. c. (synops.) 

 p. 37. 



Marshes, stagnant waters and rivulets ; forming a green stratum 

 on mud, stones, dead leaves, &c. Spring. Near Edinburgh, Mr. 

 Arnott and Dr. Greville. — Under the microscope, the frustula are 

 found to be very minute, perfectly plane, and united into more or less 

 complete circles of various sizes, partly hyaline, partly of a yellowish- 

 green colour. When dry, the mass is dark-green and somewhat glist- 

 ening. 



Tribe XXV. Cymbelleje. 



Frustula elliptical. 

 107. Gomphonema. Ag. Gomphonema. 



/ : rvstul<i BubgeminatQ, terminating a very Blender, simple or 

 \)\-,\\H\wi\ filament. — Name ; yo/Apo;, a lOftfy*, and vr.ux, B thread; 

 from the shape of the frnstoles of the filaments, 



1. G. iiiiitutissiininn, Grev. (smallest Gomphirmiiia); minute 



oehraeeoni somewhat scattered entangled, stipes Bubramoeej 

 frustula linear wedge-shaped. Grev. Crypt. II. t. 24 -\.f. 1. 



Pools and hikes, investing the submerged stems of grasses, sticks, &c* 

 with a lax cottony covering. Duddingston Loch, Dr. Greville. Spring. 



— The presence- oi'thi-, plant BVeS a yellowish appearance to the water. 



The stipes is sometimes simple, sometimes once or twice divided; the 

 frustula ooited or separated, hyaline at the base and apex, but contain* 

 log a green granular mass in the centre. The whole i> scarcely more 



than a line in height 



■J. <i. IhrkcWyii, Grev. ( Mr. Hcrkefcy's ( »<">/. hnunnu ); tufted 



