132 NATURAL HISTORY OF 



pinnfe are alternate, they are given off " so nearly in 

 a single line as generally to fold together/' 



SuB-DivisioN : STATOPLEA GYMNOCARPA. 

 Genus V, Halicornaria, Bush. 



Like Aglaophenia, but without corhulce or other pro- 

 tective case for the gonophores. 



This genus, originally proposed by Mr. Busk with a 

 somewhat different diagnosis, was established by Prof. 

 Allman (Hydroida of the Porcupine, Zool. Soc. Trans., 

 1874) for those zoophytes, otherwise resembling Aglao- 

 phenia, which have no protective corbulae or cases. 



1. H. PENNATULA, E. and 8. 



Sertularia pennatula {E. and S., Bosc, Flem), Plumu- 

 laria pennatula {Lamh., Flem., G. J., B. Q. C, D. L., 

 P. H. G., McA.), Aglaophenia pennatula {Lamx., Ag., 

 'T.H.). 



Hab. : Very rare. On the South Coast. Height 

 3 — 6 in. 



This is the " Sea-pen or Feather Coralline " of E. 

 and S., in whose notes it is described as being "as 

 remarkable for the elegance of its form as for its like- 

 ness to the feather of a pen.^' In this species, which 

 is very rare, the pinnae are alternate and very close 

 together, so as often almost to overlap. The calycles 

 are crowded together on the upper side of the pinnae, 

 and each of them is denticulated at the sides and pro- 

 tected by a spinous process, which rises to some distance 

 over the orifice and then bends over it. These spines 

 vary in curvature. In one of my specimens the spines 

 on the pinn» on one side of the stem are all almost 



I 



