SUB-KINGDOM III. CCELENTERATA. 



Classes. 



1. Hydrozoa. 



Sub-Classes. 



1. Hydromedusa?. 



2. Scyphomedusae. 



3. Siphonophora. 



4. Graptolitoidea. 



5. Stromatoporoidea. 



Orders. 



Sub-Orders. 

 Actinaria. 

 Antipatharia. 



3. Madreporaria. 



1. Aporosa. 



2. Rugosa. 



3. Fungida. 



4. Perforata. 



(1. Zoantharia. 

 2. Alcyonaria. 



THE Co3lenterates include the jelly-fishes, corals, and 

 allied forms. They differ from the sponges in the absence 

 of a canal-system, in the middle layer of the body wall 

 being very thin, and in the presence of thread-cells or 

 nematocysts. This sub-kingdom can be divided into two 

 classes, (1) the Hydrozoa, (2) the Actinozoa. 



CLASS. HYDROZOA. 



The Hydrozoans are characterised by not having the 

 digestive tract separate from the general cavity of the body 

 (ccelenteron), and by the latter not being divided into 



