(114) 



slightly swollen, with a strong conical, coloured, three jointed spine 

 projecting upwards from its outer edge, its base hardly reaching to the 

 lower edge of the dissepiment. Substance rather rigid, and not very 

 tenaciously, at least in the older parts, adhering to paper. Colour, a 

 dark pui-]Dlish red, fading to a pale red or reddish white in decay. 

 Favellaj roundish, single, lateral on the upper branchlets, with a single 

 involucral spine, strongly involute, about one and a-half times the 

 diameter of the favellee. 



A beautiful and definite, although one of om* most common species ; 

 scarcely less common on the east coast than C. ruhrum, nor is it less omnico- 

 lous in its habitat, growing from high-water"mark almost to the lowest level 

 of spring-tides ; on rocks only covered for a short time at high-water, as 

 well as in tide-pools where it is never dry, and on stones, old shells, and 

 freqviently parasitical on the smaller Algse. When found on rocks, how- 

 ever, it more frequently grows on the shells that generally cover it than 

 on the rock itself. 



On the east coast in many places, where it grows in great profusion 

 on rocks covered with mussel-shells and barnacles, near high-water 

 mark, it forms dense hemispherical tufts, from one to two inches in 

 diameter; but on sand -covered rocks it grows parasitically in equal 

 abvindance and much greater luxuriance, often from three to five inches 

 in length. In shady tide-pools it often attaches itself to Corallina 

 and other Algae. The larger specimens may be readily mistaken for 

 C st7-ictum, but the lateral spines will readily distinguish them. In these 

 it very closely resembles C. fiageUiferum, but the habit, slender fila- 

 ments, and transparent articulations will at once separate it from that 

 species ; while its single, erect, robust, three-jointed, colom-ed spines will 

 be easily distinguished from the numerous pellucid, single-jointed, squar- 

 rose spines of C. echionotum. The favellaj and tetraspores when present, 

 and they are not rare, will afford additional characters. 



EXPLANATION OF PLATE CVII. 



Fig. 1. — Ceraviimii acanthonotum, natural size. 

 2. — Apex of a Lrancli. 

 3. — Joints with tetraspores. 

 4. — Tetraspore from same. 

 5. — Branchlet witli favellse. All magnified. 



