120 TUBULAKIID^E. 



by a delicate membranous sheath ; flask-shaped, with two 

 sets of filiform tentacles the oral short, in several verticils 

 placed close together and surrounding a prominent probos- 

 cis, the aboral longer, in a single series near the base of 

 the body ; gonozooids on branched peduncles, borne on the 

 body of the polypite at the base of the lower tentacles, free 

 and medusiform when mature. 



Gonozooid : Umbrella (at the time of liberation] nearly 

 globular ; manubrium with a simple mouth ; radiating canals 

 4<, terminating in four marginal bulbs, from one of which, 

 in some cases, a single tentacle is developed, while in others 

 each bulb bears a tentacle. 



THE Steenstrupia of Forbes is founded on the free zooid 

 of this genus. 



Corymorpha is distinguished by a number of remarkable 

 characters. Its solitary habit it shares with only two 

 Hydroid genera beside (Myriothela and Hydra}. The 

 membranous sheath which invests the coenosarc is a modi- 

 fication of the more usual polypary ; while the free basal 

 extremity, with its appendages, adapted to root the zoo- 

 phyte in the sand, is a unique peculiarity. The gono- 

 zooids, like those of Clavatella, are not contained in a pro- 

 tective sac (ectotheca) , but are naked throughout the course 

 of their development. 



Schmidt has constituted the genus Amalthaa for two or 

 three species in which each of the four bulbs on the margin 

 of the umbrella gives origin to a fully developed tentacle. 

 In all other points they seem to agree with Sars's genus 

 Corymorpha ; and I cannot allow that a mere difference in 

 the number of arms, unaccompanied by any other structural 

 peculiarity, is a sufficient ground for detaching them from 

 it. I have therefore made the diagnosis of the present 

 genus broad enough to include them. 



