116 



CCELENTERATA 



FAMILY 5. ^QUOREIDAE. 



Trophosome: mostly unknown. Gonosome: medusa often of large 

 size and more or less disc-shaped, with from 8 to 100 radial canals; 

 gonads usually ribbon-like; 8 or more lithocysts; 8 or more marginal 

 tentacles: about 7 genera. 



Key to the genera of ^Equoreidae here described : 



Oi Manubrium short. 



6j Radial canals 8 to 20 1. HALOPSIS 



6 2 Radial canals 16 to 100 2. ^QUOREA 



Oa Manubrium large and long 3. ZYGODACTYLA 



1. HALOPSIS A. Agassiz. Medusa disc-like in adult and hemispher- 

 ical in youth; radial canals 12 to 20 in 4 groups; marginal lithocysts, 



tentacles and cirri numerous ; 

 manubrium short with 4 oral 

 lobes: 1 species. 



H. ocellata A. Ag. Di- 

 ameter 7 cm.: New England 

 coast; rare. 



Fig. 195 &quorea tennis (Mayer). 



2. -ffiQUOREA Peron and 

 Lesueur. Hydroid form mi- 

 nute and mostly unknown; 



medusa disc-shaped or hemispherical, with a short, wide manubrium 

 and numerous radial canals, lithocysts, and tentacles: 10 species. 



A. (Ehegmatodes A. Agassiz) tennis 

 A. Ag. (Fig. 195). Radial canals 20 to 

 40 with an equal number of gonads; ten- 

 tacles numerous, long 'and slender, with a 

 spur above the base of each; diameter 3 

 to 10 cm.: Vineyard and Long Island 

 Sounds; very irregular in its occurrence. 



A. albida (A. Ag.) Radial canals 

 and tentacles 80 or more in number; 

 above each tentacle is a spur; diameter 7 

 cm.: New England coast. 



3. ZYGODACTYLA Brandt. Hydroid 

 form unknown; medusa arched and with 

 a large sac-like manubrium with exten- 

 sive frilled oral lobes extending beyond 

 the velum; subumbrella with rows of warts between the radial canals: 

 1 species. 



Z. groenlandica (Peron and Lesueur) (Fig. 196). The largest Amer- 

 ican hydromedusan, measuring 12 cm. or more in diameter; radial canals 



Fig. 196 Zygodactyla graenlan- 

 dica (Mayer). 



