118 THE MARINE BOTANIST. 



on the east coast of North America in several 

 places^ Dr. Harvey says it is an abundant species. 



P. ohscura. Spreads over marine rocks at half- 

 tide level ] also parasitical on Fuci and on some of 

 the small algse. Jersey. Sidmouth. '^ Tufts of 

 small size densely matted tog-ether. Articulations 

 visible in all parts of the frond. Colour a dark 

 brown-red." 



P, simulans. Grows on rocks, &c., in tide- 

 pools, near low water-mark. Annual. Summer. 

 Rare. Bathing Cove and Tor- Abbey Rocks, Tor- 

 quay. Bovisand, near Plymouth. Falmouth. Jersey, 

 Valentia, Kerry. Skaill, Orkney. This species 

 was for some time confounded with P. spinulosa, 

 and described as such ; in microscopic character it 

 differs from that in having- twelve siphons or tubes 

 surrounding the central cavity ) in the true 

 P, spinulosa there are but four. In outward aspect 

 it is exceedingly variable, sometimes resembling 

 P. subulifera, and at others P. nigrescens ; in allu- 

 sion to these deceptive appearances it received the 

 specific name of simulans, Mrs. Griffiths de- 



