156 .CAMPANTJLAlirUXE. 



4. O. DICHOTOMA, Linnaeus. 



" SEA-THREAD CORALLINE," Ellis, Corall. 21, pi. xii. figs. , A. 

 SERTULARIA DICHOTOMA, Linn. Syst. 1312 ; Ellis $ Soland. Zooph. 48. 

 LAOMEDEA DICHOTOMA, var. a, Johnston, B. Z. 102, pi. xxvi. figs. 1, 2; Alder, 

 North, and Durh. Cat, Trans. Tynes. F. C. iii. 121. 



Plate XXVIII. fig. 1. 



STEM filiform, slender, nearly straight, irregularly branched, 

 ringed above the origin of the branches, of a deep horn- 

 colour ; branches suberect, often very long, and more or 

 less ramified, ringed at intervals, a single calycle in the 

 axils ; HYDROTHEC^E alternate, broadly campanulate and 

 deep, polyhedral above, each side corresponding with a 

 very slight sinuation of the margin, borne on ringed ped- 

 icels, which vary in length from 4 or 5 to as many as 

 16 rings; GONOTHEC.E axillary, slender, smooth, widen- 

 ing from the base upwards, and terminating above in a 

 raised, somewhat conical aperture. 



GONOZOOID. UMBRELLA very shallow, without thread-cells; 

 MANUBRIUM trumpet-shaped ; MARGINAL TENTACLES (at 

 the time of liberation) 16. 



IT is difficult to settle the synonymy of this species, as the 

 descriptions of the older authors are wanting in minute- 

 ness and precision, and several kindred forms have been 

 confounded under the Linnean name dichotoma. I have 

 retained it for the present form, which^ seems to corre- 

 spond best with the Ellisian and Linnean species, and have 

 only given such synonyms as are undoubted. 



0. dichotoma is of comparatively humble size, and has 

 none of the subverticillate mode of growth which gives so 

 much beauty to its near ally 0. flabellata. The stems and 

 branches are almost straight ; the latter are irregularly dis- 

 tributed, often very long and straggling, and more or less 

 branched. They are intermingled, on the main shoots, 

 with simple ringed pedicels bearing a single calycle. The 



