of British Hijdroid Zoophytes. 357 



Zealand. Like our species it is tridentate ; but on a careful 

 comparison of the two, I find that the southern form differs from 

 ours in the following particulars. It is of smaller size and more 

 compact mode of growth ; the cells are more closely set, smaller, 

 shorter, broader at the base, and attached for a greater part of 

 their length, besides having some rib-like thickenings of the 

 walls, which are not to be found in the northern species. There 

 are likewise occasionally two oi" three cells together witl.out a 

 joint. The ovicapsules are very similar, but the aperture is not 

 so much produced, and is conical, not funnel-shaped. Upon the 

 whole I think there can be little doubt that the two species are 

 distinct. The form is at least new to the British seas. 



The cells of this s])ccies do not bulge out below as in S. poly- 

 zonias, and the capsules are narrower and much more strongly 

 and regularly ribbed across, with a funnel-shaped aperture, having 

 a smooth, everted rim. 



Sertularia tenella, u. sp. PI. XIII. figs. 3-6. 

 Sertularia rugosa, var., Johnst. Brit. Zoopb. 62. f. 8 c. 



Minute, creeping, throwing up short unbranched or slightly 

 branched stems, which are slender, zigzagged, and jointed 

 above each cell : cells alternate, rather distant, elongate, 

 barrel-shaped, finely wrinkled across; the aperture erect, 

 patent, squared and four-toothed. 



Length |^ to 1 inch. 



Parasitical on Plumularia falcata and other zoophytes, but not 

 common. 



This pretty little species is smaller and more delicate in all its 

 proportions than S. rugosa, with which it has hitherto been con- 

 founded. The cells are more erect, narrower, and more closely 

 and regularly ribbed or wrinkled across; the wrinkles generally 

 rising a little opposite each angle ; they are six or seven in this 

 species — in S. ruc/osa three or four. The aperture is erect, 

 patent, and conspicuously squared and four-toothed : in S. ru- 

 gosa the aperture is much less prominent, and is always bcmt 

 outwards. The stem of S. tenella is slender, seldoiu exceeding 

 half an inch in length, and most frequently unbranched : it is 

 waved or zigzag, bearing a cell at each angle : opposite each cell 

 there is a joint, above which the cell is much constricted and 

 slightly ringed or twisted. The cells are more distant than in 

 <S'. rugosa, in this resjjcct resembling S. pohjzonics, but are more 

 slender and elongated than in eithi;r species ; they are thin, 

 delicately wrinkled transversely and produced a good deal at the 

 top. The aperture is closed by a quadripartite operculum, open- 



