14 CXELENTERATA AND 



(hood) over the sense capsules and with or without mar- 

 ginal sense bodies ; with hell-cavity, the entrance into 

 which is partially closed by a velum. 



Order II. Track ymed usee. Bell-shaped, often disk- 

 like bodies. Four or eight sense capsules with or without 

 hood. Bell-cavity with velum. 



Order III. Siphonophora. Tubular or bag-like bod- 

 ies. Many individuals of different shape and function 

 united in a colony. With or without bell-shape and ge- 

 latinous appendages. When present, these resemble those 

 of Hydroida. 



Order IV. Acraspeda. Disk-shaped bodies with four, 

 eight or sixteen marginal sense-capsules. No bell-cavity. 

 No velum. 



Order V. CtenopJiora. Single polar sense-capsule with- 

 out hood. Locomotion by means of eight meridional 

 rows of vibratile flappers on outside of body. 



Order I. Hydroida {free) . 



A. Without sense capsules ; sexual organs never free 

 from the base of the proboscis. 

 I. Tubes four, unbranched. 



No tentacles Pennaria. 



One tentacle Hybocodon. 



Two tentacles Stomatoca. 



DinemateHa. 

 Four tentacles Sarsia. 



Dipurena. 



Eetopleura. 



Zanclea. 

 More than four single tentacles. Turns. 



Dysmorphosa. 



Staurophora. 



Calicopsis. 



Modeeria. 



