256 THE MARINE BOTANIST. 



awl-shaped prickle, springing from the outer edge. 

 This last character separates it from C. echionotum, 

 in which the spines are scattered all round the 

 joint, " pointing in various directions, like the spines 

 of a sea-urchin ; " likewise C. ciliatum, the spines 

 form a regular whorl round the joint, and from C. 

 jiabelligerum, the only other species with unilateral 

 spines, it may at once be known by its transparent 

 articulations, and its very different growth. Grows 

 on exposed rocks near low water-mark, and on 

 the smaller algae. Annual. Summer and autumn. 

 Not uncommon. Torbay. Plymouth. West of 

 Ireland, common. Youghal. Appin, Argyleshire. 

 Aberdeen. 



CERAMIUM CILIATUM.--REGULARLY. 

 WHORLED CERAMIUM. 



Grows in dense bundled tufts, of a paler purple 

 than the preceding plant, and known from C. 

 echionotum by its regular whorl of prickles, all 

 pointing upwards, and not irregular, inserted and 



