ADDENDA. 261 



Genus NETRIUM (Xag.). 

 Netrium oblongum (De Bary) Liitk. (vol. i, p. 66). 



Var. aiigustatum West. 



N. oblongum var. miyiixtntiiiH West, Clare Island Alg. 1912, p. 9. 



Cells distinctly narrower than in the type. 

 Length 123 ^ ; breadth 23 p. 

 IRELAND. Clare Island, Mayo ! 



Var. brevius West. 



N. obl'iiiijinii var. In; vius \\V>t, Clare Island Alg. 1912, p. 9. 



Cells about 3| times longer than broad. 

 Length 86 y. ; breadth 25 ;JL. 

 IRELAND. Clare Island. Mayo ! 



v 



Genus PENIUM Breb. 



Following the investigations of Dr. LiitktMniiller the following 

 species must be removed from the genus Petnmn (see Liitk. 

 ' Gattung Penium; 1905). 



PENIUM JEXXERI Ralfs (vol. i. p. 77) must now be placed in 

 Cylindrocystis (vide supra, p. 260). 



PENIUM LIBELLULA (Focke) Xordst. (vol. i. p. 73) and P. 

 NAVICULA Breb. must be transferred to the genus Clostermm 

 (n'de infra, pp. 261, 262). 



PEXIUM ADELOCHOXDRUM Elfv. (vol. i, p. 93), P. MOOREAXUM 

 Arch. (vol. i, p. 80), P. CLEVEI Lund. (vol. i, p. 87), P. SUBTILE 

 W. & G. S. W. (vol. i, p. 92), P. LAGEXARIOIDES Roy (vol. i. p. 93), 

 P. CUCURBITIXUM Biss. (vol. i, p. 94). P. CURTUM Breb. (vol. i, 

 p. 97), P. IXCOXSPICUUM (vol. i. p. 101) and P. MIXUTUM (Ralfs) 

 Cleve (vol. i, p. 101) are all to be removed to the genus Cosmarium 

 Corcla (vide infra, pp. 266-268). 



Genus CLOSTERIUM Nitzsch. 

 Closterium Libellula Focke (vol. i, p. 73). 



clnsterium Libellula Focke, Phys. Stud. 1847, p. 58, t. 3, f. 29; Liitkem. 



Gattung Penium 1905, p. 337. 

 Petrium Libellula (Focke) Xordst in W. & G. S. W. Brit, Desm. vol. i, p. 73. 



