348 Mr. J. Ralfs on the Diatomacese. 



Meloseir(B they are attenuated; the cells too are not divided as 

 in Meloseira by lines, either single or double. 



" The above I think are some of the principal differences be- 

 tween the Conferva which has received Mr. Thompson's name 

 and the Meloseira, and these are in my opinion too considerable 

 to admit of its holding a place with these. Would it not be more 

 correct to place it with the species of the genus Lynghya V 



* Filaments moniliform ; frustules united in pairs. 



1 . M. nummuloides, Ag. Frustules spherical, having a line near each 



end, but less strongly marked than the central one. Ag. Syst. 



p. 8 ; Consp. Diatom, p. 65 ; Kutz. in Linnaea 1833, p. 70. fig. 72; 



Grev. in Hook. Br. Fl. vol. ii. p. 401 ; Harv. Br. Alg. p. 195. 



M. discigera, Ag. Syst. p. 8 ; Berk. Br. Alg. p. 31. t. 11. fig. 2 ! 



M. Borreri, Wyatt, Alg. Damn. no. 232 ! Conf. nummuloides. 



Dill. p. 45. t. B. Conf. moniliformis, Jurg. Dec. 1. no. 7 ! Gal- 



lionella nummuloides. Eh. Die Infus. p. 167. t. 21. fig. 1 ; Pritch. 



Infus. p. 199. G. moniliformis, Bailey, American Bacil. part 2. 



p.4. pi. 11. fig. 3. 



In the sea or in brackish water. Margate, Rev. M. J. Berkeley ; 

 river Dart, Mrs. Wyatt ; salt marshes near Larne, co. Antrim, and 

 near Dublin, Mr. D. Moore. Penzance ; Bangor, N. Wales. 



It is brown when recent and becomes green in drying. Fila- 

 ments free, slender, moniliform, constricted between each pair of 

 the frustules. Frustules globular, united in pairs, and each di- 

 vided into hemispheres by a central line, and crossed by a fainter 

 line at each end. 



Plate IX. fig. 1. Meloseira nummuloides ; a, frustules deprived of colour- 

 ing matter ; b, different stages, showing the mode of growth ; c. dotted lines, 

 marking new hemispheres ; d, new hemispheres just formed. 



2. M. Borreri, Grev. Frustules rather longer than broad, cylindrical, 

 rounded at the ends, with a central, strongly marked line. Grev. 

 in Hook. Br. Fl. vol. ii. p. 401 ; Harv. Br. Alg. p. 196. Conf num- 

 muloides, Eng. Bot. t. 2287 ! (bad). 



On marine algse. Shoreham Harbour, Mr. Borrer ; Chichester 

 Creek, Mr. Jenner. Penmaen Pool near Dolgelley. 



This species much resembles the preceding, but is I believe 

 distinct. The filaments are stouter ; the frustules rather longer 

 than broad, cylindrical, with their ends less convex, and marked 

 only with a central line. Sometimes the ends at their junction 

 are compressed, and then the frustules appear angular. In this 

 character it seems to approach the M. moniliformis; the ends 

 however of the frustules in that species are figured by Ehrenberg 

 as truncated cones — more convex therefore than those of M. num- 

 muloides , and consequently still more so than those of this plant. 



Plate IX. fig. 2. Meloseira Borreri. 



3. M. glohifera, Harv. Frustules nearly globular, with numerous 



