198 INVERTEBRATE ZOOLOGY 



Class 1. Calcarea. Sponges with calcareous spicules and of simple 

 structure. Ex. Grantia. 



Class 2. Hexactinellida. Glass sponges with six-rayed silicious 

 spicules. Ex. Euplectella. 



Class 3. DemospongicE. Massive sponges with either silicious spic- 

 ules or spongin fibers or both. Ex. Spongilla. 



Subphylum II. Cnidaria. Coelenterates provided with nettle 

 cells. 



Class 1. Hydrozoa (Hydromedusae). Hydroid polyps and jelly- 

 fish, the former without mesenterial ridges and the latter with a 

 velum. 



Order 1. Hydrariae. Freshwater hydroids of simple structure. 

 Ex. Hydra. 



Order 2. Hydrocorallinae. Coral-like marine hydrozoa i is. Ex. 

 Millepora. 



Order 3. Tubulariae. Hydroids without hydrotheca; medusae 

 with gonads on the manubrium. Ex. Pennaria. 



Order 4. Campanulariae. Hydroids with hydrotheca; medusae 

 with gonads on the subumbrella. Ex. Obelia. 



Order 5. Trachomedusae. Hydroids (when present) minute and 

 of simple structure ; medusae usually large with gonads on the sub- 

 umbrella. Ex. Gonionemus. 



Order 6. Narcomedusae. Hydroids wanting ; medusae with lobed 

 rim. Ex. Cunina. 



Order 7. Siphonophora. Eree-swimming colonial hydrozoans. Ex. 

 Physalia. 



Class 2. Scyphozoa (Scyphomedusae). Hydroids and jelly-fish, the 

 former with mesenterial ridges and the latter without a velum and 

 often of large size. Ex. Aurelia. 



Class 3. Anthozoa. Sea anemones and corals ; solitary or colonial 

 polypoid cnidarians without medusoid generation. 



Order 1. Alcyonaria. Anthozoans with eight mesenterial ridges 

 and eight pinnate tentacles. Ex. Corallium. 



Order 2. Zoantharia. Anthozoans with numerous mesenterial 

 ridges and numerous simple tentacles. Ex. Metridium. 



Subphylum III. Ctenophora. Coelenterates with eight bands of 

 ciliated ridges on outer surface. Ex. Mnemiopsis. 



