Marine Algce of the Orkney Islands. 323 



algologists consider the new genus as merely a species of C'/lIi- 

 thamnion, while they think that Call, corijmhosum and Call, 

 versicolor should be regarded as distinct species. Mr Batters "svhen 

 here lately picked out several specimens of Call, versicolor from u 

 parcel of Callithamnia dredged in Kirkwall Bay, the greater number 

 of Avhich he at once pronounced to be Call, corymhosurn." 



140. Callitharmiion arbuscTila (Dillw.), Lyngb. 



Ou vertical rocks in the shade, usually a little below half-tide 

 level, in places which are uncovered for some hours daily. Peren- 

 nial, but in poor condition and stunted during winter. Fruit 

 from April to August. Skaill, West Mainland ; Rousay ; Birstane 

 Pier, &c. 



GRIFFITHSIA, Ag. 



141. Griffithsia setacea (Ellis), Ag. 



la deep, shaded pools between tide marks ; on the perpendicular 

 sides of exposed rocks in the shade near low-water mark ; also in 

 deep water. Perennial. Fruit in April, May, and June Dredged 

 otf Crossiecrown, Kirkwall Bay, b\ fathoms ; Kousay. Common 

 in bays. 



142. Griffithsia corallina (Linn.), Ag. 



On rocks at low-water mark, and at a greater depth ; also 

 epiphytic on Algae. Always submerged. Annual. Fruit in 

 summer. Dredged off Crossiecrown, near Kirkwall, b\ fathoms ; 

 Carness, very fine ; Rousay. Common in bays. 



PTILOTA, Ag. 



143. Ptilota elegans, Bonuem. [Ptilota sericea, Gmel.) 



On shaded rocks and in dark crevices from a little below 

 half-tide level to low-water mark. Left uncovered by the tide 

 in the shade for several hours daily. Perennial Fruit in spring 

 and summer. Eday, in a narrow dark chasm east of the island ; 

 Carness, opposite Thieves' Holm, fine. 



144. Ptilota plumosa (Linn.), Ag. 



In deep water ; epiphytic on Laminaria hyperharea. Perennial. 

 Fruit in spring and summer. Common, and often very fine. 



DXJDRESNAYA, Bonnem. 



145. Dudresnaya coccinea (Ag.), Bonnem. 



Usually either on rocks near low-water mark, or, more generally, 

 in 4 to 10 fathoms. Annual. Summer. Found in Kirkwall 

 Bay by Mr PoUexfen. 



GLOIOSIPHONIA, Carm. 



146. Gloiosiphonia capillaris (Huds.), Carm. 



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

 water. Seldom in pools between tide marks. Somewhat uncertain 

 in its appearance. Annual. June to September. Fruit in July 



