34 



Hah. On shells and stones from deep water, common, 

 from Falmouth to Plynioutb. 



This species varies from one to six inches in heif/;!)t, and 

 is delicate and drooping when large. The trunk is divided 

 by septa, between each of which are phiced one or two rings 

 of an inter-articular substance, which is well figured by 

 Johnston; each internode gives olf one pinna at its upper 

 end, which rests on a protuberance of the stem, and gives 

 it a waved appearance. The joints of the pinna3 are also 

 separated by the inter-articular rings. The cells are distant 

 small, cup-shaped, situated on a protuberance of the inter- 

 node, and their apertures are plain and even. Between the 

 cells are two minute hollow teeth, visible only under a high 

 magnifier. 



Dr. Johnston, in his references, has not considered that 

 Ellis' figure, pi. xi., no. 16, a A, refers to this species; or at 

 least he has not referred to it, as he has to the figure at plate 

 38. But no. 16, at plate xi., is a very good likeness of those 

 I have found growing on shells on this coast, and figure A, 

 appears to be a magnified representation of the same; though 

 Dr. Johnston thinks both refer to Plumularia pinnata : in 

 P. pinnata, the pinnae arise from each internode, and the 

 vesicles are strongly toothed, while in P. setacea, as in Ellis' 

 figure, there is only one pinna arising from each internode. 

 Dr. Fleming has united them under one name. There 

 appear to be three varieties of this species which has probably 

 given rise to this confusion. 



The first variety, the longest with the shortest pinna?, is 

 figured by Johnston at pi. xviii., figs. 4, 3, and generally 

 grows on stones : 



The second, on shells, feather-like in appearance, and like 

 the figure of Ellis' at pi. xl., no. 16, a, on which 1 have found 

 abundance of vesicles like those figured surrounding the 

 stem, and not placed in the axillae of the pinna? : 



The third, always parasitical, and inost commonly on the 

 Plumularia frutescens, is figured by Johnston, pi. xviii., fig. 3, 

 and Ellis' Corallines, pi. 38, fig. 4. 



BRANCHED SEA BRISTLES. P. Pinnata. "Stem 



plumous ; the pinnae alternate; cells rather distant, one on 



each inttrnode, campanulate, leaning, the mouth entire ; 



vesicles obpyriforn), strongly toothed above. DiUenius." 



Fucoides setis minimis indivisis constans, Raii, Synop., 



vol. 1, p. 39. Sert. pinnata, Turton's Lin., vol. 4, p. 683. 



Stewart's Elcm., vol. 2, p. 446. Plum, pinnata, Johnston 



in Mag. Nat. Hist., vol. 6, p. 498. Aglaophenia pinnata, 



Lamouroux's Cor. Flex., p. 172. Plum, piuuala, Johnston's 



Brit. Zuoph,, p. 145, pi. xvii,, figs. 4 and 5. 



