1 64 



PHYLUM CCELENTERA. 



median canal. At the proximal free end there is a minute triangular or 

 dagger - shaped body the sicnla which represents the embryonic 

 skeleton. Some reproductive bodices or gonangia have been found. The 

 animals were probably free-swimming in muddy seas, and of a Hydro- 

 medusan nature. 



FIG. 79. Graptolites. 

 III. Didymograptus ; IV. Tetragraptus. 



Class II. SCYPHOMEDUS^: ( = Acraspeda). 



Jelly-fish with gastric filaments, sub-genital pits, and no velum 



(1) Lucernariae . Sedentary forms. Lucernaria. Haliclystns. 



Depastrum. 



(2) Discomedusae. - - Active forms, often with complicated life 



history. Aurelia, Pelagia, Cyanea, Rhizostoma. 



(3) Cubomedusae. Forms with broad pseudo- velum, and other 



peculiar features. Charybdea. 



(4) Peromedusae. Forms with four tentaculocysts only. Pericalpa. 



Class III. ANTHOZOA ( = Actinozoa). 



Polypoid forms with well-developedgullet and septa, and circumoral 



tentacles, 

 (i) Zoantharia or Hexacoralla. 



(a) Actiniaria. Sea-anemones. Actinia, Ammonia, TeaJia, 

 Cerianthus. 



