NORTHUMBERLAND AND DURHAM. 113 



3. S. RUQOSA, Linn. 



Johns. Brit. Zooph., 63, t. x., f. 4 — 6. 

 Parasitical on other zoophytes from low-water mark to 

 deep water; frequent. 



4. S. TENELLA, n. sp. PI. IV., f. 3 — 6. 



Minute, creeping, throwing up short unbranched, or Slightly 

 branched stems, which are slender, zig-zagged, 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. 

 Sertularia mgosa, var. Johns. Brit. Zooph., 62, f. 8 c. 

 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^ w^ith 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; there are six or seven in 

 this species — in >S'. rugosa three or four. The aperture is 

 erect, patent, and conspicuously squared and four-toothed ; 

 in S. rugosa the aperture is much less prominent, and always 

 bent outwards. The stem of S. tenella is slender, seldom 

 exceeding half an inch in height, and most frequently un- 

 branched ; it is waved or zig-zagged, bearing a cell at each angle ; 

 opposite each cell there is a joint, above which the stem is much 

 constricted, and slightly ringed or twisted. The cells are more 

 distant than is S. rugosa^ in this respect resembling S. polyzonias; 

 but they are more slender and elongated than in either species. 

 The aperture is closed by a quadripartite operculum, opening in 

 segments, as in Camp, sijringa^ but here the segments are fewer, 

 corresponding Avith the angles of the mouth. S. rugosa has a 

 similar operculum. The ovicapsules, for a knowledge of which I 

 am indebted to the Rev. T. Hincks, scarcely differ from those of 



5. polyzonias and S. rugosa^ but are perhaps a little more produced 

 at the top. The polypes appear to be yellow or orange coloured. 

 Specimens of S. tenella occur in which the creej^ing fibre throws 



