30 THE VOYAGE OF H.M.S. CHALLENGER. 



Sub-Order III. CTENOSTOMATA, Busk. 



Ctenostomata, Busk, Hincks, Smitt, Auctt. 

 Halcyonellea and Vesicularina, Jolinst. 



Character. — Zocecial orifice simply circular, bilabiate (■?) or quadrangular; retractile; 

 border contractile, furnisbed witb a setose or membranous fringe or velum. Zoarium 

 corneous or membranaceous, or carnose ; never calcified. No marsupial or appendicular 

 organs. 



Division L— HALCYONELLEA. 



Halcyonellea, Ehrenberg, Hincks. 

 Polyzoa carnosa, Gray. 

 Alcyonidulse, Jobnst. 

 Haley onellas, Smitt. 



Character. — Zoarium membranous or carnose, or semigelatinous, developed by 

 continuous gemmation of the zooecia from eacb other. 



This division, embracing in Mr. Hincks' classifica;tion the genera 



Alcyonidium, 



Flustrella, 



Arachnidium, 



is represented in the Challenger collection by a single species referable to Alcyonidium. 



Family I. Alcyonidul^. 



Alcyonidulx, Couch. 

 Ealcyonellex, Smitt. 

 Alcyonidiidx, Hincka. 



Character. — Zooecia more or less closely united, immersed in an expanded and 

 adherent gelatinous crust, or forming an erect, cylindrical or compressed zoarium ; orifice 

 closed by the invagination of the tentacular sheath. 



The Family here contains : — 



1. Alcyonidium, Lamouroux. 



(1) Alcyonidium Jlustroides, n. sp. (PI. X. figs. 13, 14). 



