PLUMULAEIA SETACEA. 297 



AOLAOPHENIA SETACEA, LtttHX. Col", flex. '271. 



PLUMULAIUA SETACEA, Lamk. An. s. Vert. (2nd cd.) ii. 165 ; Johnst. B. Z. 97, 

 pi. xxii. figs. 3-5 [not fig. 81, p. 465] ; Agassi;, N.H.U.S. 358. 

 PENNAIUA SETACEA, OJcen, Lekrb. Nat. 94. 



Plate LXVI. fig. 1. 



SHOOTS very delicate ; STEM slightly waved and regularly 

 jointed; pinna alternate, one to each internode, origina- 

 ting immediately below the joint, composed of longer and 

 shorter internodes, placed alternately, the former bearing 

 the calycles ; HYDROTHEC/E small, with an even rim, very 

 distant, separated by two joints ; NEMATOPHORES elongate, 

 two abreast behind and above the calycle, two in a line 

 beloiv it, one at the origin of the pinnae, and one on each 

 segment of the stem ; GONOTHEC^E borne in the axils of 

 the pinncs ; female ampnllate, smooth, produced above 

 into a tubular neck, with a plain orifice ; male linear- 

 oblong, slender, smaller than the female, less produced 

 above, and tapering to a fine point, with a very minute 

 terminal aperture. 



P. SETACEA varies considerably in size; it is commonly 

 from an inch to an inch and a half in height, but some- 

 times attains a larger growth. A variety occurs which is 

 much and irregularly branched, and of luxuriant habit. 

 Its arborescent shoots are very unlike the neat little 

 plumes of the more usual form ; but the minute characters 

 of the two are identical. This variety, which I have only 

 received from Cornwall, I believe to be from deep water. 

 In rock-pools, and when fringing the stems and branches 

 of other zoophytes (it has a marked predilection for An- 

 tennularia], P. setacea is of extreme tenuity and delicacy. 

 In other situations it is frequently of robuster habit, the 

 main stems being stout and of a deep horn-colour. 



This species is one of the commonest and prettiest of 

 the littoral Hydroids. Forests of its little plumes over- 



