Marine Algce of the Orkney Islands. 331 



Family.— GELIDIACE^. 



GELIDIUM, Lamour. 



197. Gelidium corneiiin (Huds. ), Lamour. 



Usually in pools and on exposed rocks at about half-tide level. 

 Perennial. Forma typiea said to be found at Linga Sound, rare ; 

 var. clavatum east side of Kirkwall Bay, 1887 (G. W. T.). 



Family.— SPOXGIOCARPEiE. 



POLYIDES, Ag. 



198. Polyides rotundus (Gm.), Grev. 



Common on sandy flat shores in pools near low-water mark. 

 Perennial. Fruit in winter. 



Family.— LOMENTAEIACEtE. 



LOMENTARIA, Gaill. 



199. Lomentaria kaliformis (Good, and Wood.), Gaill. (Chylocladia 



kaliformis, Hook. ) 



On rocks and stones in deep Avater, and sometimes between tide 

 marks. Annual. Spring and summer. Bay of Work, good ; 

 Rousay, near Broch, good ; very fine in Kirkwall Bay. When 

 growing in still water from 2 to 3 feet in length, according to 

 M'Bain. 



200. Lomentaria ovalis (Huds.), Endl. {Chylocladia ovalis, Hook.) 

 On rocks and stones in pools between tide marks. Annual. 



Fruit in summer. Occurs at Papa-Westray. 



Family.— RHODOMELACEvE. 



ODONTHALIA, Lyngb. 



201. Odonthalia dentata (Linn.), Lyngb. 



On stones and rocks from a little below low-water mark to deep 

 water. Perennial. Fruit in winter. Common. 



RHODOMELA, Ag. 



202. Rhodomela lycopodioides (Linn.), Ag. 



Foi'ma ti/picrr common on stems of Laminaria hyperhorea. 

 Biennial. Fruit in June, July, and August. Broch of Deerness, 

 line. 



202a. Rhodomela lycopodioides, var. ^ laxa, Kjellm. 



I found this well-marked form in 1887 in pools, Bay of Carness, 

 due south from Hellyar Holm. On my forwarding a specimen to 

 Professor Kjellraan, Upsala, he identified it as his var. jS laxa, 



