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. Demospongie. Massive sponges with either silicious spic- 
ules or spongin fibers or both. Ex. Spongilla. 
Suppyytum II. Cnidaria. Coelenterates provided with nettle 
cells. 
Class 1. Hydrozoa (Hydromeduse). Hydroid polyps and jelly- 
fish, the former without mesenterial ridges and the latter with a 
velum. 
Order 1. Hydrarie. Freshwater hydroids of simple structure. 
Ex. Hydra. 
Order 2. Hydrocoralline. Coral-like marine hydrozoans. Ex. 
Millepora. 
Order 3. Tubularia. Hydroids without hydrotheca; meduse 
with gonads on the manubrium. Ex. Pennaria. 
Order 4. Campanularie. Hydroids with hydrotheca; meduse 
with gonads on the subumbrella. Ex. Obelia. 
Order 5. Trachomeduse. Hydroids (when present) minute and 
of simple structure; medusz usually large with gonads on the sub- 
umbrella. Ex. Gonionemus. 
Order 6. Narcomeduse. Hydroids wanting; medusze with lobed 
rim. Ex. Cunina. 
Order 7. Siphonophora. Free-swimming colonial hydrozoans. Ex. 
Physalia. 
Class 2. Scyphozoa (Scyphomeduse). 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. 
Suspuyium III. Ctenophora. Coelenterates with eight bands of 
ciliated ridges on outer surface. Ex. Mnemiopsis. 
