TRACHOMEDUSAE 



119 



medusa which buds from the hydroid, bell-shaped, with 4 radial canals 

 and 8 tentacles: 1 species, in fresh water. 



M. ryderi Potts (Fig. 199). Hydroid cylindrical, with a crown of 

 nematocysts around the mouth, .5 mm. 

 long, often branched near the base 

 into two equal individuals; medusa .3 

 mm. high and .4 mm. wide at birth; 

 no sense organs or gonads observed : 

 on stones in rapid streams in Phila- 

 delphia; Germany. 



3. CRASPEDACUSTA Lankester 

 (Limnocodium Allman). Trophosome: 

 minute, without tentacles. Gonosome: 

 disc-like medusa with 4 radial canals; 

 tentacles numerous, of several dif- 

 ferent lengths; lithocysts numerous; 

 manubrium long: 2 species; distribu- 

 tion world-wide. 



C. sowerbi* Lank. (Fig. 200). 

 Diameter about 12 mm. ; gonads 4, 



suspended from the radial canals, greenish in color; oral lobes, large, 



^ ^ crenulated, greenish; bell translucent 



"^ -"-. ; ** with a faint bluish tint ; 4 long, about 



** > ? 4 



28 shorter and 192 shortest tentacles: 

 in a fresh-water aquarium in Wash- 

 ington containing tropical water lilies; 

 also in similar places in London, Mu- 

 nich, and Lyons; probably introduced 

 from South America. 





Fig. 200 Craspedacusta sowerbi 

 (from Mayer). 



FAMILY 2. AGLAUKIDAE. 



Trophosome: wanting. Gonosome: 

 medusa with 8 radial canals, free 

 lithocysts and gonads in berry-like 

 masses and numerous tentacles: 5 

 genera. 



Key to the genera of Aglaundae here described : 

 a l Gonads 8. 



&! Gonads borne on manubrium 1. AGLAUBA 



& 2 Gonads borne on radial canals 2. AGLANTHA 



a 2 Gonads 2 3. PEBSA 



* See "Occurrence of Fresh-water Medusa, Limnocodium, in the United States," 

 by C. W. Hargitt, Biol. Bull., Vol. 14, p. 304, 1908. 



