Plumulaiiia. Z. HYDROIDA. 147 



belong to PI. i)iiiiiata Aglaopheiiia sotacea, Lainoitr. Cor. Flex. 172. 



Coiall. 70 Pluimilaria setacea, Lam. Aniin. s. Vert, ii, 129. "ide 



edit. ii. 165. Flem. Brit- ATiim. 547. Templeton in Mag. Nat. Hist. 



ix. 467. Starh, Elem. ii. 440. Bisso, V Eiirop. merid. v. 313 



La p. setacee, Blainv. Actinol. 177. 

 Hab. Parasitical on other corallines, not uncommon. At Brigh- 

 ton on flag, Lister. Frequent near Hartlepool, growing on the roots 

 of the Palmated Fucus, Hogg, On scallop shells in the Frith of Forth, 

 Jameson. Berwick Bay, G. J. Belfast Lough, Templeton. Co^k 

 Harhour, Thompson. 



In favourable sites this coralline will sometimes attain a height of 

 six inches, but in general it is smaller, more delicate, and less plumous 

 than PI. pinnata with which it has been confounded, although its 

 habit and minuter characters prove it to be quite distinct. The stem 

 is somewhat waved and regularly jointed, the joints consisting of two 

 or three I'ings, and immediately under each joint the internode is 

 somewhat enlarged in consequence of the pinna originating there, a 

 single pinna only springing from under each joint, whereas in P. 

 pinnata, as already remarked, three pinnae proceed from each inter- 

 space, the joints of which, moreover, consist of a single fracture. The 

 pinnae are jointed like the stem, celliferous, the cells small and dis- 

 tant. At the base of each there is a minute tubular process (abor- 

 tive cell ?), visible only with a high magnifier. The vesicles are el- 

 liptical, smooth, with a narrow plain orifice, .and originate in the axils 

 of the pinnae. — " The ova within were opake and yellow. Its polypi 

 had from sixteen to nineteen arms, and when they were full blown it 

 was an object of remarkable beauty." Lister. 



6. P- Catharina, stem plumous^ the pinna opposite, hent 

 inioards ; cells distant, campamdate icith an even margin ; vesi- 

 cles scattered, pear-shaped, smooth. G. J. 



Vignette, No. 8, page 79. 

 Plumiilaria Catharina, Johnston in Mag. Nat. Hist. \\. 498, fig. 61, 62. 



Hah. On old shells, corallines, and ascidia in deep water. At 

 Scarborough, rare, Mr Bean. Frith of Forth, Dr Coldstream. 

 Frequent in Berwick Bay. 



This equals PL pinnata in size and delicacy, but diifers from it very 

 obviously in having opposite pinnae, which, instead of being arched, 

 bend inwards, so as to render the general form of the coralhne con- 

 cave on a front view ; an appearance produced by the pinnae origi- 

 nating, not from the sides, but from the anterior face of the stem. 

 The stem itself is straight or slightly bent, jointed, pellucid, filled 

 with a granular fluid matter ; and, in which it diff"ers from its 

 congeners, bearing cells, there being always one at the base and be- 

 tween the insertion of the pinnae, and generally another on the 



