THE INVERTEBRATE LEGIONS 



97 



Trachyline hydrozoans are all medusas and look like true jellyfish. (One 

 species, Geryonia, is shown in Color Plate 10.) They have no polyp stage, 

 contrary to most hydrozoans, and are small to moderate in size, not reaching more 

 than 4 inches across the bell. They may be distinguished from true jellyfish by 

 the presence of a shelf called the "velum," projecting inward from the lower 

 bell margin Cfigs- 26 and 27). 



Fig. 28. Stinging coral, Millepora, takes on a number of forms including that of 

 these foot-high hlades, hut it is most easily recognized hy its mustard-yellow color and 

 knohhy textiire. In the background is a large hush gorgonian. 



