134 Z. HYDROIDA. Sertularia. 



is a larg-e specimen, from the Frith of Forth, in which they are re- 

 markably zig-zag or kneed, so as to give it a pecuhar character and 

 appearance. In the same collection are specimens from the Cape of 

 Good Hope, which differ in no respect from those of our shores. 



15. S. AUGE'STE A, polT/pidojn cauliferous ; cells nearly oppo- 

 site or suhalternate, urceolate, acutely pointed^ the upper half di- 

 varicated ; vesicles oval. Merret. 



Plate XII. and Plate XI. Fig. 3, 3. 

 Corallina miiscosa, alterna vice denticulata, ramulis in creberrima capilla- 



menta sparsis, Rail, Syn. i. 36, No. 17. Muscus maiinus denticulatus 



minor ramulis in creberrima eapillamenta sparsis, Pluknet, Phytog. tab. 



48, fig. 3 Muscus marinus minor denticulis alternis, Morris. Hist. 



Plant. Oxon. iii. 630, tab. 9, fig. 4 Squirrel's-tail, Ellis, Corall. 6, 



No. 4, pi. 2, fig. c, C. Sertidaria cupressina, /3, Lin. Syst. 1308 



S. argentea, Ellis and Soland. Zooph. 38. Tiirt. Gmel. iv. 677. Wern. 

 Mem. i. 564. Berk. Syn. i. '216. Tiirt. Brit. Faun. 213. Stew. Elem. 

 ii. 442. Bosc, Vers, iii. 108- Lam. Anim. s. Vert ii. 117. Lamonr. 

 Cor. Flex. 192, Corall. 84. Hogg's Stockton, 32. Templeton in lib. 



cit. 468. Johnston in Trans. Newc. Soc. ii. 258, pi. xi. fig. 4 La 



S. argentee, Blainv. Actinol. 480 Dynamena argentea, Flem. Brit. 



Anim. 544. 

 Hab. In deep water. On oysters and other large bivalved shells, 

 as also on the stalk of Laminaria digitata, common. 



Polypidom from 6 to 18 inches high, caulifei"ous, the stem percur- 

 rent, fihform, waved or straight, smooth, of a dark brown colour, di- 

 vided at rather wide but regular intervals by an oblique joint, clothed 

 with short panicled dichotomous branches which spread out on every 

 side, and being all of the same size or nearly so, (excepting at the 

 bottom where they are less branched and smaller, and at the top where 

 they also frequently become gradually shortened,) the whole coralline 

 assumes somewhat of the shape of a squirrel's tail, and has given ori- 

 gin to its English name. Two branches usually arise from each in- 

 ternode of the stem, and they come off in such a manner that four 

 or five of them complete a whorl. The polype-cells on the stem are 

 alternate, appressed, and appear to be less than those on the branches, 

 which are placed in two I'ows with their orifices inclined to one side ; 

 they are bellied like a Florence-flask with a narrow divaricated neck 

 terminated with a small oblique aperture : on some of the branchlets 

 every pair is separated by a joint or stricture, while on others several 

 pairs occur in succession without the interference of such a structure. 

 Vesicles scattered, oval, smooth, attenuated at the base. 



In young specimens of an inch or two in height the polypidom is 

 simply pinnate, and as it rises the branches gradually divide into more 



