PLUMULARIA SIMILIS. 303 



Its plumes arc very compact, slightly recurved, and some- 

 what wide. Dr. Johnston has exaggerated the amount of 

 resemblance between it and P. sctacea. Besides the dif- 

 ferences in size and habit, and in the form and position of 

 the capsules, there is a striking dissimilarity in the details 

 of structure, in the shape of the calycles, the jointing of 

 the stem and pinnse, and the number and character of the 

 nematophores. The latter in the present species are of 

 the simple type, whereas in P. setacea they are compound, 

 affording a very good illustration of the bithalamic form. 

 The female capsule encloses a single large sporosac, con- 

 taining many ova. The spinous processes, which form a 

 crest upon the longitudinal ridges f, vary in the degree of 

 development, and are sometimes of very considerable 

 length. 



Hub. On stone and weed, between tide-marks and in 

 shallow water ; not uncommon. It shows a decided pre- 

 ference for Zostera marina and Chorda filum. 



5. P. SIMILIS, Hincks. 



PLUMULARIA SIMILIS, Hincks, Cat. Devon & Cornw. Zooph., Ann. N. H. 



(ser. 3) viii. 257, pi. vii. figs. 3, 4. 

 SETACEA, Landsborough, Pop. Hist. B. Z. pi. ix. figs. 26, 2G*. 



Plate LXV. fig. 3. 



SHOOTS simple, slender, white, or of a pale horn-colour, and 

 attaining a height of about an inch and a half ; STEM 

 jointed, internodes long and of equal width throughout ; 

 pinnae alternate, one below each joint, set forward on 

 the stem; HYDROTHEC.E rather large, curving outwards 

 towards the top, entire, very distant, always separated 

 by two joints ; NEMATOPHORES minute, simple, one below 

 each calycle ; GONOTHECJE ovate, elongate, tapering below, 



t "Vosiculis cristato-serratis." Lamarck. 



