1 20 NATURAL HISTORY OF 



Devon {T.H.), Nortliumberland (Aid), Wick {C. TV. P.), 

 Isle of Man (Forbes), North of Ireland [Thomjpson) , 

 Blackpool, the Mersey [A. 8. P.). Height 4—6 in. 



This is the " Sea Spleenwort or Polypody " of Ellis. 

 It has " two rows of straight, hollow branches a little 

 compressed, which are placed on the middle stem 

 opposite to each other in a parallel and alternately 

 pinnated form, like the leaves of Polypody/^ — Ellis. 

 Upon these branches the cells are placed in a double 

 row, apparently sunk into the branch. The stem is of 

 a dark horn colour, and regularly jointed between each 

 pair of branches, which do not seem to be continua- 

 tions of the stem, but to be jointed to it. 



FAMILY IX. PLUMULARID^. 



Hydrothecce sessile and unilateral. Zoophyte fur- 

 nished with nematophores (minute calycles containing an 

 extensile offshoot from the coenosarc and frequently hear- 

 ing thread cells). Polypites with a single wreath of 

 filiform tentacles round a conical proboscis. Gonozooids 

 always fixed. — T. H. 



This is the first hydroid family upon which a report 

 has been issued in connection with the " Challenger 

 Expedition." Prof. Allman, who is investigating the 

 hydroids of that collection, has (pai*t xx. Challenger 

 Reports), in his report on the Plumularidce, fully de- 

 scribed the characteristics of the family ; and I have, 

 therefore, in the following descriptions adopted the 

 divisions and genera favoured by him. 



The family is divided as follows : — 



